Marine Ostracoda ofthe Galapagos Islands and Ecuador

Transcription

1 Zoo/o,$cal Journal ofthe Linnean Society (19811, 73: With 45 figures Marine Ostracoda ofthe Galapagos Islands and Ecuador RAYMOND H. BATE, JOHN E. WHITTAKERANDCAROLA. MAYES Department ofpalaeontology, British Museum (Natural History), London S W7 5 BD Acceptedforpublication October 1980 Marine algae collected from rock pools on Hood, Fernandina and Mosquera, in the Galapagos Islands, have provided a fauna of 26 ostracod species ofwhich 14 are new. One genus, belonging to the Ilemicytheridae, is also new and appears to be endemic to the Islands. From two littoral algal samples collected from Punta Canoa and San Pedro beach, Ecuador, an assemblage of some nine species, four of which are new, is also described. Two ostracods: Touroconcha lapidiscola and Loxoconchu (Loxocorniculurn) lenticulozdes, are the only species so far known to be present both in the Galapagos Islands and off the coast of Central and South America. One species: C~therelloideapraecipua recorded from off Tobago and Clipperton Islands may be present in the Galapagos but this has not definitely been c-onlirmcd. The evolution in the Gulf CoadCaribbean region of several ostracods and their wbsequrnt dispersal westwards is discussed. KEY WORDS :- Ostracoda- Platycopina- Podocopina- Cytheracea- Galapagos - Ecuador CONTENTS Introduction I Systematic descriptions Origin of the Galapagos ostracod fauna Acknowledgements References , INTRODUCTION The Galapagos Islands, with their unique fauna and flora, have interested scientists since the time of Darwin. Thus, when one ofus (J.E.W.)visited the islands in 1974 the possibility of collecting marine ostracods was explored and permission Present address: 16 Pymmes Green Road, London N /8 1/ $02.00/ The Linnean SocietyofLondon

2 9 R. H. BATEETAL

3 OSTRACODS FROM GALAPAGOS AND ECUADOR 3 obtained to collect a small number of algal samples.* These were collected from littoral rock pools on three islands (see Fig. 1): on 28 November from Punta Espinosa (Fernandina Island); on 30 November from Mosquera, a small islet lying between Baltra and North Seymour Island, and on 1 December from Punta Suarez (Hood Island). No temperature or salinity measurements were taken at the time but sea temperatures taken in Academy Bay, Santa Cruz Island (Harris, 1974) averaged 23OC through November and December over the period We can assume, however, that the temperature in the rock pools would fluctuate and for part of the day be significantly above 23OC. Normal marine salinities can be assumed for the rock pools as they were not tidal. The ostracod fauna described here is thus indicative of those species living during the period of collection and does not necessarily represent the total fauna present at other times of theyear. In order to compare the Galapagos ostracods with those living on the coast of Ecuador, the fauna from two Ecuadorian littoral samples is included here. The samples, again of marine algae (extremely rare in the littoral zone of Ecuador), were collected on 22 October 1974 from Punta Canoa (Grid reference ) and from San Pedro beach (Grid reference ) on 31 October 1974 (see Fig. 1). The Galapagos Islands, lying on the equator some 600 miles (1000 km) west of Ecuador, are of volcanic origin. The oldest dated lavas are Pleistocene, 1.4 million years old (McBirney8c Williams, 1969). Despite their equatorial position the islands are surrounded by relatively cold waters brought up from the Antarctic by the Humboldt current (dashed line in Fig. 1, inset). Should this current fa(l -as occasionally happens-then warmer water flows south from the region of the Gulf of Panama and surrounds the islands. This phenomenon, known as El Niiio is rare, but nevertheless may have a bearing on the composition of the Galapagos ostracod fauna, possibly explaining how some species, or their ancestors, arrived in the area from the Americas. Previous ostracod research for the Galapagos Islands is restricted to an early paper by Triebel (1956), three papers by Pokorny (1968, 1969, 1972) and two papers on Radimlla by Benson (1967a,b). No complete faunal study has been attempted prior to the present paper. In Ecuador there has been a total absence of marine ostracod research, the nearest (geographically) are the studies of Hartmann (1959, 1962, 1965) from Chile and San Salvador and by Ishizaki 8c Gunther ( 1976) from the Bay of Panama. The Galapagos Islands have been given names by both the British and the Spanish, the latter names being made official in 1892 by the Ecuadorian government who own the islands. Some of the British names are still preferred locally, however (e.g. Hood, rather than Espaiiola) and it is the local usage that is followed in this paper. Apart from the systematic study of the ostracod fauna it is profitable, even on only a few samples, to speculate about the dispersal route and probable source of the fauna-this we undertake in the final section. All the ostacod material described in this paper has been deposited in the collections of the British Museum (Natural History). Reference numbers commencing 1978 refer to specimens in the Department ofzoology. * 25g of filamentous algae were collected for each sample, the algae being preserved by the addition of ship 5 alcohol. The ostracods were dissected six months later.

4 R. H. BATE ET AL. SYSTEMATIC DESCRIPTIONS Suborder Platycopina Sars, 1866 Family Cytherellidae Sars, 1866 Genus Cytherelloidea Alexander, 1929 Cytherelloidea sp. aff. C.praecipuavan den Bold, 1963a (Fig. 2A) Remarks. Cytherelloidea praecipua van den Bold, 1963a was first recorded from Recent coral sands from Tobago, West Indies and subsequently from the Pacific, from Clipperton Island (Allison& Holden, 197 1). Clipperton Island is situated in the eastern Pacific to the north-east of the Galapagos Islands (see Fig. 1, inset). The single carapace recorded here although comparable in many ways with C. praecipua, does not have its distinct anterior marginal rim nor its anterior marginal dentition. As we have only a single specimen we prefer, in this case, to record it simply as above. Cytherelloidea sp. aff. C. praecipua of Swain & Gilby (1974) has a more positive rib pattern than the Galapagos specimen and is not considered to be conspecific at this time. Dimensions. 1978: 181, carapace, length 0.57 mm; height 0.34 mm; width 0.21 mm. Distribution and ecology. From Mosquera Islet on marine algae. Cytherelloidea parapraecipua sp. nov. (Figs 2B-J, 3,4A,B) Derivation of name. Greek, para, close to; pertaining to the considered relationship of this species to C. praecipua van den Bold, 1963a. Diagnosis. Carapace rectangular, largely smooth-shelled but having small number of rather large pits arranged in clusters on lateral surface. Two ribs extend forward from posterior end of shell while third rib is situated in antero-dorsal region. Holotype. Q carapace, 1978: 182, San Pedro beach, Ecuador. Paratype. Q carapace, 1978: 183, San Pedro beach, Ecuador. Distribution and ecology. Recorded only from the type locality on marine green algae. Description. Carapace rectangular in outline with flattened posterior end and broadly rounded anterior: anterior margin may be dentate but not strongly so. Dorsal outline sinuous, distinctly concave in the smaller left valve anterior to midpoint. Shell surface has two ribs extending forwards from the posterior end, the lower rib extending into the anterior half, the upper restricted to the posterior half. A third rib, obliquely inclined and slightly sinuous in outline, is positioned in the anterodorsal region of the shell. Shell surface smooth except for weak striations anteriorly and posterodorsally and for a small number of rather large pits that are clustered into groups spaced over the surface-but not at valve centre. Normal pore canal apertures simple with tasellate setae. Internally the hinge is represented by the smooth edge of the smaller left valve that fits into a deep groove extending around the inner margin of the larger right valve. Dorsally a distinct tooth-like projection of the left valve is situated just behind mid-point (Fig. 2C) that articulates with the deep socket found in the right valve (Fig. 2E). The muscle scars are a rosette of 11 scars. The first antenna has seven podomeres, the first two

5 OSTRACODS FROM GALAPAGOS AND ECUADOR Figure 2. Cylherelloidea sp. affc. praeczpua. A. Left sideofmalecarapace, 1978: 181 (X 831. Cytherelloidea purupruedpwl sp. nov. B, C. External and internal views, female LV., holotype 1978: 182 (X 83). D, E. External and internal views, female RV., holotype 1978: 182 (X 83). F. Seta and normal pore, holotype 1978: 182 (x2.5k). CJ. 2nd Antenna; 1st antenna; maxilla and mandible, holotype 1978: 182 (x 230).

6 R. H. BATE ET AL Figure 3. Cytherelloidea parapraecipua sp. nov. Female LV., paratype 1978:183, dorsal view to show tooth-like projection ofdorsal margin. (proximal) being geniculate-three short, thick setae are present on each podomere. The second antenna with uniramous, geniculate 1st and 2nd podomeres, the remaining podomeres biramous, ciliate; outer ramus with two segments, inner ramus with three segments. Mandible palp with comb-like row of ventrally projecting setae and terminating in a long seta. Maxilla with three masticatory lobes and three-segmented palp, the proximal two segments each with four short setae; terminal segment ending with claw-like seta and having two shorter setae above and behind and a row of comb-like setae. Respiratory lobe large with more than 20 long setae. The first thoracic appendage biramous; proximal segment with vibratory plate bearing long setae, distal segment elongate, terminally rounded and bearing a lateral row of long setae and a second row of shorter setae. Furcae spatulate with about 12 spines. Dimensions. Holotype: 1978: 182, 9 carapace, disarticulated, LV., length 0.60 mm; height 0.33 mm; RV., length 0.61 mm; height 0.35 mm. Paratype: 1978: 183,q carapace, disarticulated, LV., length0.61 mm; height0.34 mm; RV., length mm; height 0.37 mm. Remarks. Like Cytherelloideapraecipua van den Bold, 1963a (recorded by van den Bold from Trinidad and Tobago, West Indies and by Allison& Holden, from Clipperton Island, East Pacific Ocean) and C. monodenticulata Holden, (from the late Cenozoic of the Hawaiian Islands), C. purupruecipuu sp. nov. possesses a dorsal hinge tooth in the left valve that articulates with a distinct socket in the right valve. This feature, previously recorded in a number of species, has been reviewed by van den Bold ( 1963a). C. parapraecipua has the rather sparse pitting present in C. monodenticulata but has a rather more positive rib development comparable with that of C. praecipua. Indeed, the illustrations of this species by Allison & Holden ( : 209) lead us to believe that C. praecipua and C. parapraecipua must be closely related, the latter differing by a reduction of the surface pitting to scattered groups of pits. In this way, C. parapraecipua also differs from C. sp. aff. praecipua of Swain & Gilby ( 1974) from off Baja California. It is considered, however, that Cytherelloidea praecipua from the West Indies and from Clipperton Island in the Pacific and C. sp. aff. C. praecipua from the Pacific coast of North America, belong to a group of closely related species that also includes C. parapraecipua and C. sp. aff. C. praecipua from the Galapagos Islands.

7 OSTRACODS FROM GALAPAGOS AND ECUADOR Suborder Podocopina Sars, 1866 Superfamily Bairdiacea Sars, 1888 Family Bairdiidae Sars, 1888 Genus Neonesidea Maddocks, 1969 Neonesidea sp. (Fig. 4 D-F) Remarks. Two single valves : , are considered to belong to a possibly new species of Neonesidea that is close to Neonesidea gierlofl (Hartmann, 1959) - a species originally assigned to the genus Triebelina and described from the coast of El Salvador. The Galapagos species differs by having a more steeply sloping dorsal margin and by lacking the ventral incurvature of N. gierlojj. Dimensions. 1978: 179, LV., length 0.70mm; height 0.37 mm. 1978: 180, RV., length 0.78 mm; height 0.39 mm. Distribution and ecology. Punta Suarez, Hood Island and Mosquera Islet, on marine algae. Genus Paranesidea Maddocks, 1969 Paranesidea sp. (Fig. 4C) Remarks. This valve possesses the typical bairdiid outline and coarse surface pitting of Paranesidea. We cannot as yet assign this single left valve to any known species. Dimensions. 1978: 178, LV., length0.88 mm; height0.53 mm. Distribution and ecology. From Mosquera Islet on marine algae. Superfamily Cytheracea Baird, 1850 Family Paradoxostomatidae Brady & Norman, 1889 Subfamily Paradoxostomatinae Brady & Norman, 1889 Genus Perspicytherois Swain & Gilby, 1974 Remarks. Externally similar in appearance to Pellucistoma, this genus differs by having all elements of the modified adont hinge smooth and by having sieve-plate pore canals. Perspicytherois sp. (Fig. 4G-L) Remarks. This species is left under open nomenclature as only two specimens have been found - it is always more difficult to assign a smooth species to a taxon than it is an ornate species when so few specimens are available. Our specimens are close to P. perspicilla (Benson & Kaesler, 1963) but have a more pointed posterior end and a more prominent hump-like dorsal outline; the anterior vestibule is also larger and the hinge has a distinct posterior tooth in the right valve. Perspicytherois perspicilla is recorded from the Gulf of California by Benson & Kaesler (1963, as ParaRrithella) and from the Pacific coast of Baja California by Swain & Gilby (1974). The genus does not, therefore, have a particularly extensive geographic range, the present species merely extending the distribution southwards into Ecuador. Dimensions. 1978: 184, RV., length 0.54 mm; height 0.30 mm. 1978: 185, LV., length 0.54 mm; height 0.30 mm. Distribution and ecology. San Pedro beach, Ecuador, on marine algae. 7

8 8 R. H. BATE ET AL. Figure 4. Cytherelloideaparapraecipva sp. nov. A, B. 1 st Thoracic appendage and furca, female holotype 1978: 182 (x 230). Parunesideasp. C. Externalview,LV., 1978: 178 (~65). Neonesideasp. D, E. External ant1 intcrnal views, RV., 1978: 180 (~65). F. LV., 1978: 179 (~65). Perspzcythemis sp. G, K. External view, RV.,(x83)andsieveplate(x 1.5K), 1978: 184. H, I,J,L. InternaIview,LV.,(x83);posteriorand anterior ends of LV., hinge (x 350) and muscle scars (x 375), 1978: 185.

9 OSTRACODS FROM GALAPAGOS AND ECUADOR Genus Paradoxostoma Fischer, 1855 Paradoxostoma galapagogrande sp. nov. (Figs 5A-M, 6A, B, 7A) Deriwation of name. Galapago + Latin, grandis, great, large. Diagnosis. Paradoxostoma with medium-sized, oval carapace, obliquely angled posteroventral border and broad duplicature having approximately three anteroventral marginal canals and four posteroventral canals. Vestibule of characteristic outline with constriction just anterior to midventral position. Copulatory appendage with broad, triangular (equilateral) distal plate and elongate curved lappet. Holotype. d carapace (disarticulated), 1978 : 192, Mosquera Islet. Material. 17 specimens from Mosquera Islet, Hood Island and Fernandina Island. Colour fspecies. Grey with darker irregular areas. Distribution and ecology. Mosquera Islet and Hood Island on marine algae. Description. Carapace oval-elongate, smaller in the male dimorph, with greatest height behind mid-point. Dorsal outline broadly convex with almost imperceptible cardinal angles. Ventral margin with shallow median incurvature. Anterior narrow, rounded; posterior broad with strongly angled posteroventral margin. Carapace slender in dorsal view. Shell surface smooth. Normal pore canal apertures simple with a slightly raised rim (Fig. 6B). Internally the hinge is a simple smooth bar having an elongate posterior socket in the left valve while the right has a corresponding dorsal groove that terminates in a triangular tooth. Muscle scars consist of four elongate adductor scars and an anterodorsal elongate scar that is probably the frontal scar. A small ocular (?) swelling (Fig. 5E, G) is present on the inside of each valve but this is not reflected in any way by an external feature and may represent the site of a muscle attachment. Duplicature broad, extending from the posterior hinge tooth/socket round to the anterior termination of the hinge (Fig. 5E, G). The duplicature has a large, deep vestibule extending the length of the duplicature and having a constriction anteroventrally (Fig.?A). Three anteroventral and four posteroventral marginal canals have been observed - those around the anterior margin being very short. The second antennae fourjointed with large basal protopodite and three endopodite podomeres of which the 2nd and 3rd are elongate; spinneret bristle composed of three segments. Mandible long and slender; maxilla with long, slender masticatory lobes, vibratory plate with setae typically rather broad and flattened, tapering distally. Thoracic appendages slender, four-jointed ; basal podomere large with well developed knee bristle in the 1st thoracic appendage of both dimorphs. Three endopodite podomeres in the 1st and 3rd appendages (Figs 5H, K, 6A). Copulatory appendage with a broad, triangular distal plate and an elongate, curved lappet (Fig. 5J). Dimensions. Holotype: 1978 : 192 (disarticulated 8 carapace) LV. length 0.52 mm; height 0.26 mm. RV. length 0.52 mm; height 0.25 mm. Paratypes: 1978: 186 (disarticulated 9 carapace) LV. length 0.62 mm; height 0.29 mm. RV. length 0.60mm; height 0.28mm. 1978: RV. length 0.59mm; height 0.27 mm. 1978: 188 (disarticulated d carapace) RV. length 0.51 mm; height 0.24 mm. 1978: LV. length 0.58 mm; height 0.27 mm. 1978: LV. length 0.58mm; height 0.27mm. 1978: RV. length 0.59mm; height 0.28 mm. 9

10 R. H. BATE ET AL. Figure 5. Paradoxostomagalopagogrande sp. nov. A. Externalview, female RV., paratype 1978: 186 (x 95). B. Female LV., paratype 1978: 189 ( ~95). C. Female RV., paratype 1978: 191 (~9.5). D. Male LV., holotype 1978: 192 (~95). E. Internal view, female RV., paratype 1978: 187 (~9.5). F. Male RV., paratype 1978: 188 ( ~95). G. Internal view, female LV., paratype 1978: 190 ( ~95). H. lstthoracic appendage, t'einale paratype 1978: 186 (x 180). I,J, K, L, M. Copulatoryappendages; Pndantenna; 1st thoracic appendage; maxilla and mandible, male holotype 1978: 192 (x 235).

11 OSTRACODS FROM GALAPAGOS AND ECUADOR 11 Remarks. Paradoxostoma galapagogrande sp. nov. is not the largest species of this genus (P. luederitrensis Hartmann, 1974 from S.W. Africa has a length of mm) but it is the larger of the two Galapagos species. Paradoxostoma romei McKenzie, 1967b from Australia has a similar carapace outline to the present species but the two are readily distinguished by the shape of the vestibule, an important diagnostic character in this genus, and the number of marginal pore canals that are longer in P. galapagogrande, shorter and more evenly spaced along the ventral margin in P. romei. Paradoxostoma galapagopawurn sp. nov. (Figs 6C-R, 7B) Derivation Of name. Galapago + Latin, parvus, small. Diagnosis. Paradoxostoma with slender, oval carapace; posterior and anterior ends tapered, rounded. Duplicature broad with large vestibule constricted in oral region. Copulatory appendage with triangular (isosceles) distal plate and sharply angled (boomerang-shaped) lappet. Holotype. 8 carapace (disarticulated) 1978 : 193, Punta Espinosa, Fernandina Island. Material. 23 specimens from Punta Espinosa, Punta Suarez and from Mosquera Islet. Colour Ofspecies. Colourless to dark grey with darker irregular areas. Distribution and ecology. Primarily from off Punta Espinosa, Fernandina Island but also recorded here from off Hood Island - on marine algae. Description. Carapace oval, elongate, tapering to rounded anterior and posterior ends but more narrowly rounded anteriorly. Shallow anteroventral incurvature; dorsal outline convex with almost imperceptible cardinal angles. Shell slender in dorsal view with greatest width median. Surface of carapace smooth with two types of simple normal pore canal (Fig. 6G, HI. Hinge weak, adont: dorsal edge of left valve fits inside the dorsal margin of the right, resting on a ledge rather than within a groove. Duplicature broad with well developed vestibule; constricted slightly in the oral region. Marginal pore canals not clear but appear to be very few in number. First antennae long and slender, six-jointed (Fig. 6K). Second antennae with large protopodite and three endopodite podomeres of which the 2nd and 3rd are elongate and appear to be fused. Spinneret bristle with three segments. Mandible long and slender. Maxilla with three slender masticatory processes; vibratory plate with approximately 12 setae. First thoracic appendage with strong knee bristle coming off distal end of basal podomere; smaller bristle coming from distal joint of first endopodite podomere. Second and 3rd thoracic legs long and slender, each with three endopodite podomeres. Copulatory organ with triangular, isoscelesshaped, distal plate and boomerang-shaped lappet. Male dimorph has a smaller carapace than female. Dimensions. Holotype: 1978: 193 (disarticulated carapace) LV. length 0.49 mm; height 0.22 mm. RV. length 0.48 mm; height 0.22 mm. Paratypes: 1978: 194 (disarticulated preadult -1 carapace) LV. length 0.48 mm; height (broken). RV. length 0.49 mm; height 0.22 mm. 1978: LV. length 0.54 mm; height 0.26 mm. 1978: RV. length 0.54 mm; height 0.26 mm. 1978: 197 (preadult -1 carapace) length 0.47 mm (valves broken). 1978: carapace, length 0.55 mm; height 0.26 mm; width 0.18 mm. 1978: carapace, length 0.53 mm; height 0.25 mm; width 0.16 mm.

12 R. H. BATE ET AL Figure 6. Paradoxostoma galapagogrande sp. nov. A. 3rd thoracic appendage, male holotype 1978: 192 (x 235). B. Normal pore canal aperture and seta, female LV., paratype 1978: 189 (x 3.75K). Paradoxostomagalupagoparvum sp. nov. C. Female RV., paratype 1978: 196 (X 95). D, I, K, L, M, N, P, Q. Right and LV. (x 95); 1st antenna; 2nd antenna; 3rd 0 thoracic appendage; copulatory appendages; maxilla and mandible (x 114), male holotype 1978: 193. E. Female LV., paratype 1978: 195 (x 95). F. Dorsal view, ternale carapace, paratype 1978: 197 (x 95). G. Normal pore canal and seta, holotype 1978: 193 (x 3.75K). H. Normal pore canal and seta, paratype 1978: 197 (X 2.75K). J, 0, R. 2nd and 1st Thoracic appendages and mandible, female paratype 1978: 114 (x 200).

13 OSTRACODS FROM GALAPAGOS AND ECUADOR pm u - U Figure 7. Duplicature and vestibule (V) ofa, Purudoxostomugalapugo~unde, female LV, 1978: 186 and B, Pur'arc~doxoslomu galapugopurvum, RV, 1978: 194. Remarks. Paradoxostoma galapagoparvum sp. nov. is, on the whole, a slightly smaller species than P. galapugogrande although some females of the present species may exceed the length of some individuals of P. galapagogrande. Although there is some similarity in outline between these two species they may be readily separated on details of the carapace (posteroventral angled margin of P. galapugogrande), shape of vestibule (Fig. 7) and shape of the distal plate of the copulatory appendage (equilateral in galapagogrande and isosceles in gatapagoparvum). The hinge of galapagoparvum is considerably weaker than in galapagogrande and lacks the terminal posterior tooth/socket of that species. 0 ther species of Parudoxostoma that have some external similarity to P. galapagoparvum are P. wuenschei Hartmann, 1974 from Angola and P. exmouthensis Hartmann, 1978 from Western Australia, but the shape of the vestibule and of the copulatory appendage serve to distinguish all three. Family Cytheruridae Muller, 1894 Subfamily Cytherurinae Muller, 1894 Genus Paracytheridea Muller, 1894 Paracytherideapinea sp. nov. (Figs 8,9A-J, 1OA-J) Derivation ofname. Pinea, Latin, with reference to the resemblance to a pine cone. Diagnosis. Carapace elongate, caudate, with fluted, 4-rayed posterodorsal swelling more strongly developed in male dimorph ; characteristic anastomosing pattern of ribs in anterior part of shell of both dimorphs with long A1 rib, sigmoid V1 rib extending just anterior to mid-length. Shell surface with small papillae and coarse reticulate pattern of striae; larger papillae surround sieve plate pore canals. Holotype. 9 carapace 1978 : 125, Punta Espinosa, Fernandina Island. Material. 16 specimens from Punta Espinosa, Fernandina Island and Mosquera Islet. Colour of species. White. Distribution and ecology. Fernandina and Hood Islands and Mosquera Islet, on marine algae.

14 14 R. H. BATE ET AL Figure 8. Diagrammatic presentation of rib-pattern in males and females of Paracytherideo pinea sp. nov. NotationofribsafterAllison& Holden(l97 1). Description. Carapace caudate, elongate with coarse ribbing as illustrated; finer ribbing (striae) produces a general surface reticulation. Shell surface papillose with a ring of slightly larger papillae surrounding the sieve-pore canal openings. Rib pattern as illustrated (Figs 8, 9A-C), the posterodorsal ribs more highly developed in the male. Posteroventral projection produces arrowhead outline to carapace in ventral view. Low eye-swelling situated just below anterior cardinal angle. Greatest length of carapace extends slightly below midpoint; greatest height in anterior half for the valve without the posterior ornamentation- otherwise the greatest height lies in the posterior half; greatest width through anterior half, Pore canals with sieve plate - the plate with pores of uniform size and a central setal aperture. Pore surrounded by a ring of six to seven papillae. Hinge entomodont rather than antimerodont, the anterior part of the median element being enlarged. Anterior hinge teeth (RV) discrete, posterior hinge teeth fused to form boss-like posterior tooth. Muscle scars not clear but situated around the rim of a deep pit that is reflected by a distinct swelling on the outside of the shell. Frontal muscle scar oval or kidney-shaped. Duplicature broad, without a vestibule. Right valve with a distinct anterior flange. Radial pore canals about in number anteriorly, curved and widely spaced. Left valve larger than the right, the free rnargin of the smaller valve fitting into a marginal groove of the left valve (Fig. 10F). First antennae with six podomeres; two long, terminal setae extend from 6th podomere, two shorter setae at distal end of 5th podomere. Second antennae well developed with four podomeres. Mandibles with four triangular teeth; maxillae with rounded branchial plate bearing 14 long setae, the setae positioned between small projections on the distal margin of the branchial plate. Masticatory processes and palp with strong, curved bristles. Thoracic limbs terminate in a long, curved, claw; brush organ of 2nd thoracic limb with long, delicate setae (Fig. 91). Male copulatory appendage not preserved. Dimensions. Holotype: 1978: 125. Q carapace (disarticulated) LV. length 0.66 mm; height 0.30 mm. RV. length 0.66 mm; height 0.30 mm. Paratypes: 1978: RV. length 0.66mm; height 0.32mm (posterior half). 1978: carapace length 0.66 mm; height0.31 mm; width 0.38 mm. 1978: 128 preadult-1 RV. length 0.58 mm; height 0.29 mm. 1978: 129 juv. car. length 0.43 mm; height 0.19 mm; width 0.28 mm. 1978: 130 preadult -1 LV. length 0.60 mm; height 0.31 mm. 1978: 138preadult-1 LV. length0.58 mm; height0.30 mm. Remarks. Paracytheridea pinea sp. nov. has a surface ornamentation that bears some similarity to that of P. longicaudata chilensis Hartmann and to P. tschoppi Van den Bold (see Allison & Holden, ; Teeter, 1975). In fact P.pinea is sufficiently

15 OSTRACODS FROM GALAPAGOS AND ECUADOR Figure 9. Puracytherideupinea sp. nov. A, D. External and internal views, male RV., paratype 1978: 126 (x 83). B, C, E-I, J. Right and LV. (x 83); 1st antenna; 3rd thoracic appendage; endopodite of left mandible; 1st thoracic appendage and brush-shaped organ (X 3 10); dorsal view of LV., female holotype 1978: 125 (x 83).

16 R. H. BATE ET AL Figure 10. Paracytherideapinea sp. nov. A, D, F, G, H. Maxilla (~310); normal pore sieve plate and seta (x 700); internal view LV. ( ~83); 2nd antenna with long spinneret bristleand mandibularpalp (x310), ternale holotype 1978: 125. B. Anterior marginal pore canals, -1 LV., paratype 1978: 138 (X 153). C. RV., -I instar, paratype 1978: 128 (x 83). E. Ventral view, juvenile carapace, paratype 1978: 129 (x 83). I, J. Anterior and posterior ends RV. hinge, male paratype 1978: 126 (X 200).

17 OSTRACODS FROM GALAPAGOS AND ECUADOR 17 close to the last named species that development of one from the other is highly probable. Paracytherideapinea differs from both species on the arrangement of the ribs (Fig. 8): P2 is reduced in P. tschoppi and larger in P. pinea. There are also differences between the species with respect to P1 (in both lateral and dorsal views); VI does not extend so far forwards in P.pinea and A1 is shorter in P. tschoppi. With respect to the appendages, the 1st antenna (antennule) possesses a different arrangement of the terminal setae from that in P. remanei Hartmann from the Red Sea. The greater development of the fluted rib pattern in the posterior half of the shell in the male dimorph gives the male a greater height for a given length than the female. Measurement of the valve without the posterior ornament reverses this and the relationship of length to height for both dimorphs is as commonly found in other podocopids. Using the ornamentation notation of Allison & Holden ( : 192, fig. 18) the rib patterns are readily distinguishable, not only between species, but between dimorphs (see Fig. 8). Family Hemicytheridae Puri, 1953 Subfamily Hemicytherinae Puri, 1953 Genus Galapagocythere nov. Gender. feminine. Diagnosis. Small, oval-rectangular Hemicytherinae with poorly defined (carapace) sexual dimorphism. Shell with distinct eye swelling situated on anterodorsal ridge; shell surface strongly or poorly ornamented. Carapace virtually equivalve with left valve projecting slightly above right dorsally; right valve larger than left ventrally. Normal pore canals with either single or tasellate seta. Hinge amphidont with all elements smooth; posterior tooth of right valve poorly subdivided. Muscle scars with one or both median adductor scars divided; three frontal scars and single mandibular scar. Distinct anterior vestibule; more than 60 straight anterior marginal pore canals. Third podomere of endopodite of mandible with large, curved seta. Copulatory appendage high-domed with triangular lappets. Type-species. Galapagocythere darwini sp. nov. Remarks. Galapagocythere gen. nov. belongs to the same group of Hemicytherinae as Heterocythereis Elofson, and Hemicytheria Pokorny, 1955 in that sexual dimorphism of the carapace is not particularly well defined. In species of Hemicythere Sars, 1925 and Aurila Pokorny, 1955, the female is commonly highdomed and oval in outline in contrast to the more rectangular male. The presence of three frontal scars and a smooth but divided posterior tooth (RV) distinguishes Galapagocythere from Hemicythere but allies it to Aurila and Radimella Pokorny, The divided posterior tooth of Aurila species is well seen in the second new species assigned here but is less well defined in the type-species. The absence of dentition on the median hinge element and the poorly defined dimorphism of Galapagocythere distinguish it from Aurila while Radimella is distinguishable by its rather quadrate shape and persistently coarse reticulate ornament. The divided posterior tooth, almost equivalve carapace and the oval-rectangular shape with a broadly convex dorsal outline, differentiate Galapagocythere from Hemicytheria and Heterocythereis. A feature of the ornament of Galapagocythere is the anterior ridge that passes through the eye swelling to bifurcate in the anterodorsal region. Phylogenetically Galapagocythere appears to hold a position halfway between Aurzla and Hemicytheria.

18 in R. H. BATE ET AL. Galapagocythere darwini sp. nov. (Figs 11A-L, 12A-K, 13A, B) Deriuation ofname. After the naturalist, Charles Darwin. Diagnosis. Species of Galapagocythere having surface ribbing restricted to peripheral areas of shell, otherwise coarsely pitted with tendency for pits to disappear medially. Posterior hinge tooth of right valve imperceptibly divided, smooth. Holotype. 8 carapaceand appendages, 1978: 131. Punta Suarez, Hood Island. Material. 11 specimens from Punta Suarez, Hood Island, Punta Espinosa, Fernandina Island and Mosquera Islet. Colour ofspecies. Red ;juveniles colourless. Distribution and ecology. Punta Suarez, Hood Island, Punta Espinosa, Fernandina Island and Mosquera Island, on marine algae. Description. Carapace subrectangular with rounded anterior and posterior margins, the latter with only a slight concavity on posterodorsal slope. Ventral margin broadly incurved; dorsal margin broadly arched, sloping more steeply to the posterior in the male: female with less strongly sloping dorsal margin, more angular posterior cardinal angle and therefore a slightly increased height in the posterior half. Greatest height of both dimorphs in the anterior half. Eye swelling distinct, situated on anterodorsal ridge that bifurcates just behind the eye. Shell surface with peripheral ridges, some reticulation posteroventrally and coarsely pitted, the pits dying out medially. Simple, normal pore canals with simple or tasellate setae. Hinge holamphidont. Duplicature broad with anterior vestibule and large number of straight, marginal pore canals. Muscle scars with upper two adductors divided and with three distinct frontal scars. First and 2nd antennae short and stubby, adapted for crawling, no swimming setae present. Endopodite of mandible with large, curved seta. Copulatory appendage high-domed with triangular lappet. Dimensions. Holotype: 1978: 13 1 (disarticulated 8 carapace) LV. length 0.45 mm; height 0.25 mm. RV. length 0.46 mm; height 0.26 mm. Paratypes: 1978: 132 disarticulated 8 carapace LV. length 0.47 mm; height 0.26 mm. RV. length 0.47 mm; height 0.26 mm. 1978: carapace length 0.50 mm; height 0.28 mm; width 0.19 mm. 1978: LV. length 0.49 mm; height 0.27 mm. 1978: LV. length 0.47 mm; height 0.25mm. 1978: 136 preadult -1 carapace (disarticulated) length 0.43 mm; height 0.25 mm. RV. length 0.43 mm; height 0.25 mm. 1978: carapace length 0.45 mm; height 0.25 mm; width 0.15 mm. 1979: 160~RV.length0.45mm;height0.25mm. Remarks. Galapagocythere darwini sp. nov. is readily distinguished from the second species of this genus (below) by the reduced ornamentation. Galapagocytherejtzroyi sp. nov. (Figs 13C-J, 14A-K) Derivation of name. After Captain Fitzroy, captain of HMS Beagle during the scientific voyage that took Charles Darwin to South America and the Galapagos Islands. Diagnosis. Species of Galapagocythere having coarse, reticulate ornament with four lateral ridges developed in upper part of carapace; hinge with distinctly divided

19 OSTRACODS FROM GALAPAGOS AND ECUADOR 19 Figure 11. Galapagocythere damhi gen. et sp. nov. A, G. External view, male LV. (x 1181 and normal pores with setae and eye swelling (x375), paratype 1978 :135. B, F. External and internal views, female LV., paratype 1978: 134 (x 120). C, E. Internal views, male L. and RV., paratype 1978: 132 (x 119). D. Right side, female carapace, paratype 1978: 133 (x 118). H, I, J. Posterior and anterior hingeelements; RV. and 1st thoracic appendage (x267), male paratype 1978: 132 (~375). K, L. Stereo-pair of copulatoryorgan, male paratype 1979: 160 (~220).

20 20 R. H. BATE ET AL. Figure 12. Ga1apagocytheredam nigen.etsp.nov.a. IstAntenna, maleparatype 1978: 132 (x 238). B-F. 2nd Antenna; 1st antenna; maxilla palp; mandibleand thoracicappendage, -1 instar, paratype 1978: 136 (x 235). G. Copulatoryappendage, maleholotype 1978: 131 ( x 250). H. Tasellatesetaandnonnal pore, male carapace, paratype 1978: 139 (x3.5k). I. muscle scars, male RV., paratype 1978: 132 (x 400). J. RV., -1 instar, paratype 1978: 136 (X 120). K. Anterior marginal canals, male RV., holotype 1978: 131 (~386).

21 OSTRACODS FROM GALAPAGOS AND ECUADOR 21 posterior tooth/socket. Frontal scar poorly divided into three. Copulatory appendage and mandible as for genus. Holotype. carapace (disarticulated), 1978: 137, San Pedro beach, Ecuador. Distribution and ecology. San Pedro beach, Guayas Province, Ecuador, on green algae. Descrzption. Carapace rectangular, very strongly ornamented with four lateral ridges that extend from the anteroventral region of the valve to the posterodorsal region, restricted to the upper half of the shell surface; lower part of shell coarsely reticulate. Right valve slightly larger than left with a concave posterodorsal slope; left valve posterior more uniformly rounded. Eye swelling distinct. Duplicature broad with marginal ridges around free margin of valve. Hinge holamphidont with all elements smooth and the posterior tooth (RV) divided; posterior socket (LV) with median tooth. Normal pore canals with upraised rim in dorsal part of carapace with simple setae but elsewhere with tasellate setae. Muscle scars with the lower of the two upper adductor scars divided; three frontal scars and a single, rounded mandibular scar. First and 2nd antennae with short, stout setae; endopodite of mandible with large, curved seta and copulatory appendage having triangular lappet. Dimensions. Holotype: 1978: carapace (disarticulated) LV. length 0.49 mm; height 0.26 mm. RV. length 0.50 mm; height 0.26 mm. Remarks. Galapagocytherejtzroyi sp. nov. differs from the type-species G. darwini primarily in the more strongly ornamented carapace. Additionally, G. jtzroyi possesses a more distinctly divided posterior tooth but agrees in all other shell and appendage details. Although only a single male carapace of G..fitzroyi has been found it is so distinct from G. darwini that its establishment as a new species is considered justifiable. The dimorphic feature of the darwini shell, the male having a more strongly sloping dorsal margin, is also present in.fitzroyi and would identify specimen 1978: 137 as a male regardless of the presence of a copulatory appendage. Genus Hemicytheria Pokorny, 1955 Hemicytheria? sp. (Figs 15A-K, 16A-E) Remarks. The genus Hemicytheria was established by Pokorny on fossil material from the Pliocene of Czechoslovakia. Recent species have been described subsequently by Hartmann ( 1962) from Chile. Examination of Hartmann s illustrations shows that the copulatory appendage of our Hemicytheria? sp. is closer to that of Hemicythere than it is to the species of Hemicytheria described by Hartmann. Having only a single carapace to examine has made it difficult to assign this species with any degree of certainty. The presence of three frontal scars certainly removes the species from Hemicythere as does the presence of a holamphidont hinge. Indeed, many of the characters of this species suggest a close affinity with Galapagocythere but this has to be discounted on caparace shape; Galapagocythere having a much more rounded shell outline, especially dorsally, lacking the strong cardinal angles of Hemicytheria? sp. Until more material becomes available this species will be assigned to Hemicytheria with a query. Dimensions. 1978: 144 (disarticulated 8 carapace) LV. length 0.47 mm; height 0.29 mm. RV. length0.47 mm; height0.29 mm. Distribution and ecology. Punta Suarez, Hood Island on marine algae.

22 R. H. BATE ET AL Figure 13. Gulupugocythere durwini gen. et sp. nov. A, B. Posterior and anterior ends, LV. hinge, male paratype 1978: 132 (x 375). Galapagocytherefitzroyigen.etsp. nov., maleholotype 1978: 137. C-F. Right and lett valves, external view and L. and RV., internal view (x 110). G, H. Anterior and posterior ends, RV. hinge (~300). I, J. Mandible and maxilla (x210).

23 OSTRACODS FROM GALAPAGOS AND ECUADOR 23 Figure 14. Galapagocytherefihroyigen. et sp. nov. male holotype 1978: 137. A, B. Posterior and anterior ends, LV. hinge (x 300). C, D. Normal pore canals and setae (x 2K). E. Muscle scars (x 350). F-K. lst, 2nd. and SrdThoracicappendages; copulatoryappendage; 2nd antennaand lstantenna(x210).

24 24 R. H. BATE ET AL Genus Radimella Pokorny, 1968 Remarks. Only four specimens belonging to three species have been found and of these only two come from the Galapagos Islands; the third was obtained from marine algae off the coast of Ecuador. Although numerous species of Radimella are known, details of the appendages have been lacking so far. Unfortunately, the samples collected for this paper were taken at a time when the populations of Radimella species were low and only one immature specimen of R. aphroditae was dissectable. From the absence of swimming setae on the 1st and 2nd antennae it is possible to suggest that Radimella is a phytal genus given to crawling over weed and is neither a swimmer nor a burrower - whether adults of this genus develop an ability to swim is not, as yet, known. Pokorny (1 968 : ) recognized two morphological groups for Radimella, the first based on R. dictyon and the second on R.ponderosa. Of the species described here R. aphroditae and R. poseidonis belong to the ponderosa-group while R. confragosa more closely relates to the dictyon-group. Radimella aphroditae Pokorny, 1969 (Figs 16J-L, 17A-K) 1969 Radimellaaphroditae Pokorny: 321, text-figs 32,33, pl. 7, fig. 3, pl. 10, fig. 3. Remarks. Two specimens have been examined, the larger being a -1 instar, assignable to R. aphroditae on the ornament although pre-adult, rather more tapered posteriorly than as figured by Pokorny. The smaller of the two specimens is, because of its size, questionably assigned to this species and it is this specimen that has provided the first record of Radimella appendages. The 1st and 2nd antennae are noticeably short and bear stout bristles; podomeres 2-4 of the 2nd antenna are fused. Mandible endopodite has curved, claw-like setae typical of the IHemicytheridae. Thoracic appendages rather short and stout. The smaller instar (1978: 141) has an hemimerodont hinge, the terminal teeth being slightly dentate while the median badgroove is smooth. The muscle scars (Fig. 18C), with the two median adductor scars divided and the frontal scar represented by three round scars, are typical of the genus. Marginal pore canals are straight and numerous but the precise number has not been observed. Dimensions. 1978: 140 preadult -1 instar LV. length 0.53 mm; height 0.33 mm. 1978: 141 juvenile carapace (disarticulated) LV. length 0.37 mm; height 0.23 mm. RV. length 0.37 mm; height 0.21 mm. Distrzbution and ecology. Punta Espinosa, Fernandina Island on marine algae and recorded by Pokorny from north of Espafiola Island (Hood Island) and from James Bay, San Salvador Island (James Island). Radimella confragosa (Edwards, 1944) (Fig. 16F, G) 1944 Hemicythereconfragosa Edwards: 5 18, pl. 66, figs For complete synonymy see Bold, 1975: 697. Remarks. Radimella confragosa was first described from the Miocene Duplin Marl of North Carolina by Edwards (dated by Hazel, 1977 as Pliocene). Subsequently the species has been recorded by several authors from Pliocene and Pleistocene sediments (see Bold, 1975: 697). The confragosa-group of species is considered by Bold to have an essentially Pliocene to Recent distribution within the Caribbean region. The specimen recorded here, which is conspecific with the holotype of

25 OSTRACODS FROM GALAPAGOS AND ECUADOR 25 Figure 15. Hemicytheria? sp., male carapace, 1978: 144. A-D. External and internal views LV. and external and internalviewsrv. (X 117). E. Normalporecanalseta(x 1.1K). F.Musclescars(X350). G. Eye node (~325). H, I. Posterior and anterior hinge elements, LV. (~325); J, K. 1st Antenna and mandible(x 260).

26 26 R. H. BATE ET AL. R. confragosa as illustrated by Bold (1975: pl. 1, fig. 31, is considered to be Recent and not derived from Tertiary sediments nearby. Dimensions. 1978: 142, carapace, length 0.49 mm; height 0.31 mm; width 0.28 mm. Distribution and ecology. San Pedro beach, Ecuador on green algae. First recorded from the Miocene of North Carolina and subsequently (Bold, 1975), from the Plio-Pleistocene of the Atlantic coastal region, U.S.A. and of the Caribbean region and from the Pliocene of Mexico. Radimellaposeidonis Pokorny, 1969 (Fig. 16H, I) 1969 Radimellaposeidonis Pokorny: 324, text-fig. 35a-d, pl. 8, fig. 3. Remarks. A single carapace, slightly smaller than the size recorded by Pokorny in his original description. Nevertheless this specimen is considered to be an adult that ornamentally agrees with the original illustration and description. Dimensions. 1978: 143, carapace, length 0.66 mm; height 0.39 mm; width 0.32 mm. Distribution and ecology. Punta Suarez, Hood Island on marine algae. Also recorded from off Hood Island (as EspaAola Island) by Pokorny. Subfamily Orionininae Puri, 1973 Genus Caudites Coryell8c Fields, 1937 Remarks. The genus Caudites has been present in the Gulf of Mexico-Caribbean area since Miocene times and appears to have originated there. According to McKenzie (1967a: 231) the genus migrated eastwards into the Australasian region but a westward migration into the Pacific is also clearly indicated. Indeed, to our knowledge, the genus is never more dominant than around the Galapagos Islands where eleven species are now known. 0 rnamentally Caudites is interesting for the persistent contrast between the left and right valves and for the variable types of normal pore setae present. Although all types of setae are not present in every species each does possess a simple as well as a more complex seta. The types of setae recognised are as follows: simple (Aagellate) - Figs 24H and 251, K; simple (spatulate) -Figs 21C, 23F, H and 275; 4-rayed - Figs 20M, 26C and 27C; 5-rayed - Fig. 24B; fish-tail- Fig 27C and multi-rayed-fig Closely related to Caudites is the genus Palaciosa that lacks the coarse ribbing of the former and appears to have originated in the Holocene off the Pacific coast of North America (Valentine, 1976). The species of Palaciosa described in this paper has tasellate normal pore setae of a type unlike any so far recorded for Caudites. Caudites albatrossi Pokorny, (Figs 17L-0,19A-H) 1972 Cauditesalbatrossi Pokorny: 274, figs 1,4a, 5,6a-d, pl. 1, fig. la,b. Remarks. Caudites albatrossi is present in two samples collected from the Galapagos Islands and, as live specimens were available, we have been able to enlarge upon Pokorny s original description. Adult specimens have the rib development as described by Pokorny while the - 1 instar (specimen 1978: 146, Fig. 17M) differs slightly in the development of a ventrolateral rib. The shell surface is typically pitted, rather more coarsely so

27 OSTRACODS FROM GALAPAGOS AND ECUADOR 27 Figure 16. Hernicytheriu? sp., male carapace, 1978: 144. A-C. 2nd Antenna; maxilla and copulatory appendage (x 260). D, E. Anterior and posterior hinge elements, RV. (x 325). Rudimella confragosa. F, G. Dorsal and let't views, complete carapace, 1978: 142 ( x 100). Radimelluposeidonzs. H, I. Dorsal and left views, complete carapace ( x 83). Rudimella uphroditue.j-l. External and internal views, LV. (x 83) and maxilla (x 3051, -1 instar, 1978: 140.

28 28 R. H. BATE ET AL. Figure 17. Hadimella aphroditae. A, B. Posterior and anterior hinge elements (x 300). C. Muscle scars (x 400). D-H. 2nd Antenna; 1st antenna; 1st and 2nd thoracic appendages and mandible (x 305). I. Normal pore canal apertures (x 7001, -1 instar, 1978: 140. J, K. LV. and RV.,juv. carapace, 1978: 141 (x 83). Caudites albatrossi. L. External view, RV., 1978: 223 (x 85). M. External view, LV., -1 instar, 1978: 146(x 85). N, 0. Maxilla(x285landnormalporecanalsandornamentation, 1978: 145 (~5501.

29 OSTRACODS FROM GALAPAGOS AND ECUADOR 29 within the depressions of the shell ornament (Figs 170, 19D). The normal pore canals of this species are of the funnel type (Fig. 19D). Hinge holamphidont; duplicature broad. Appendages dissected from the -1 instar are as follows: 1st antenna with six podorneres, the proximal two geniculate and the 4th and 5th fused. The last four podomeres each possess a short, stout, bristle. Second antenna is thick-set with the first two podomeres geniculate and podomeres three, four and five fused. Third podomere has a short, stout, distal bristle while the fourth podomere has a longer bristle that extends beyond the short terminal bristle of the appendage. Spinneret bristle long, slender and jointed. Although this is a pre-adult specimen the spinneret bristle is of the type found in males of this genus; the instar is considered, therefore, to be an immature male. The mandible has six teeth while the first podomere of the endopodite has two curved, slender bristles and the 2nd podomere has a single, very prominent, curved, ventral bristle and three very long bristles on the dorsal side. The distal podomere terminates with three radiating bristles of almost equal length. Maxilla with palp arid three masticatory processes all terminating in short bristles; respiratory plate with bristles of moderate length. Second thoracic appendage with tour podorneres and a terminal claw. Dimensions. 1978: 145, carapace (disarticulated) LV. length 0.59 mm; height 0.31 rnm. RV. length 0.59 mm; height 0.28 mm. 1978: 146, -1 instar, LV. length 0.49 mrn; height 0.26 mm. 1978: 223, RV. length 0.60 mm; height 0.27 mm. Distribution and ecology. Recorded here from off Hood Island and Mosquera Islet on marine algae and by Pokorny from north of Hood Island (Espafiola Island) and from Baha de la Academia, Santa Cruz Island. Again, the present distribution matches that previously recorded. Caudites asymmetricus Pokorny, (Figsl9I-M, 20A-M, 21A-C) 1972 Caudites asymmetricus Pokorny: 298, figs 3, 4K, 18a-c, 19, 20, pl. 3, fig. 3a, b, pl. 5, fig. la, b. non 1977 Cauditesasymmetricus Hazel: 374,377,378,fig. 7f. Remarks. Caudites asymmetricus was first described from the Galapagos Islands by Pokorny but subsequently a species bearing the same name was illustrated (but not described) by Hazel (1977) from the Croatan Formation (U. Pliocene to L. Pleistocene) of N. Carolina. As Hazel s species is not conspecific, it is a homonym (Hazel s illustration shows the caudal process terminally flattened while the postero-vertical and ventrolateral ridges are more irregular than in Pokorny s material); subsequently it was renamed (but not described) by Cronin & Hazel ( 1979) as C. paraasymmetricus. This species from N. Carolina is, however, sufficiently close to be considered ancestral to C. asymmetricus Pokorny, a situation paralleling that ofradimella confragosa (see Fig. 16G, F). Caudites asymmetricus Pokorny is strikingly asymmetrical when seen in dorsal view (Fig. 19K) ; laterally the left valve has a strong postero-vertical ridge and, extending from it, a short ventrolateral ridge. In the right valve the postero-vertical ridge is practically non-existent and an oblique median ridge extends down from the posterodorsal region. Shell surface pitted, coarsely so in patches. Funnel pores (Fig. 20M) have a branched (4-rayed type) seta; other pores havingaraisedrim (Fig.

30 30 R. H. BATE ET AL. Figure 18. Attached areas (aa) in four species of Caudites and one of Palaciosa. A, C. tricortata. B, C YyininPlricus. C, C. sanctaecrucis. D, C. croca. E, P. cracenta. 2 1 C) have flat setae that become subdivided along their edges but particularly terminally. Some simple apertures may also have an associated node (Fig. 19M). No sieve plates have been observed although Pokorny records them for this species. Muscle scars have the two central adductors divided as is the median frontal scar. Hinge holamphidont. The flange here is remarkable in that it appears to be ridged at low magnifications (Fig. 205) but under higher magnification is seen to be constructed of brush-shaped bundles of calcite fibres. This feature has also been noted among other Galapagos species of Caudites but never so well developed as here. The use of this flange structure to the animal is not clear at the moment but, like other marginal features of ribbing or dentition developed in different genera, may be directed towards holding the valves firmly together when closed. Sexual dimorphism of the carapace is not discernible although males are readily identifiable internally by the presence of a copulatory appendage and a longer, more slender, spinneret bristle on the 2nd antenna. Without appendage detail the only difference between the sexes appears to be that in females the RV has the same height as the LV; in males it is slightly less. The height for both valves is measured just behind the eye node. Dimensions. 1978: carapace (disarticulated) LV. length 0.63 mm; height 0.34mm. RV. length 0.63mm; height 0.31 mm. 1978: carapace (disarticulated) LV. length mm; height 0.32 mm. RV. length 0.61 mm; height 0.32 mm : carapace (disarticulated) LV. length 0.63 mm; height 0.33mm. RV. length 0.62mm; height 0.32mm. 1978: 150 9? RV. length

31 OSTRACODS FROM GALAPAGOS AND ECUADOR 31 Figure 19. Caudites albatrossi, carapace, 1978: 145. A-H. Externalviews, R. and LV. ( ~85); 2nd antenna (~285); normal pore canal (x1.3k); mandible, 2nd thoracic appendage and 1st antenna (~285); internal view, RV. ( ~85). Caudites asymmetricus. I. Female LV., 1978: 151 ( ~83). J, L. Internal and external views female RV., 1978: 150 (~83). K. Dorsal view, male carapace, 1978: 152 ( ~83). M. Muscle scars, male LV., 1978: 149 (~350).

32 32 R. H. BATE ET AL 0.63 mm; height 0.32 mm. 1978: 151 $?? LV. length 0.65 mm; height 0.35 mm. 1978: carapace, length 0.63 mm; height 0.33 mm; width 0.23 mm. Colour ofpecies. Reddish-brown, Distribution and ecology. From Mosquera Islet on marine algae and recorded by Pokorny from off Espaiiola (Hood) Island. Caudites croca sp. nov. (Figs 18D, 21D-J, 22C, D, 23A-J) Derivation of name. Croca, mediaeval latin, meaning a shepherd s crook, after the crook-shaped posteroventral rib on the left valve. Diagnosis. Caudites having sinuous postero-vertical rib from which extends, in left valve, a crook-shaped ventrolateral ridge that is absent in right valve. Both valves have long median ridge that becomes impersistent in region of muscle scars and, in left valve, forks at its anterior end well back from anterior margin; in right valve median ridge joins anterior marginal rim. Over 50 straight, anterior marginal pore canals, some branching. Holotype. 9 carapace, 1978 : 154, Punta Suarez, Hood Island. Material. 1978: 153 and 155, Hood Island and Mosquera Islet. Colour of species. Shell transparent, body reddish-brown. Distribution and ecology. Found only from off Hood Island and Mosquera Islet on marine algae. Descr$tion. Carapace with long, virtually straight, dorsal margin in left valve; slightly curved in the right with a strong incurvature above the eye swelling. Ventral margin broadly concave medially, convex posteriorly. Anterior margin broadly rounded; posterior end caudate. Anterior marginal ridge discontinuous ; postero-vertical ridge sinuous, terminating ventrally in the left valve in a crookshaped ventrolateral ridge; in the right valve the postero-vertical ridge terminates ventrally in a blind end, there being no ventrolateral ridge. Median ridge in the left valve extends across the muscle scar node (where it is rather poorly developed) to terminate anteriorly in a bifurcating ridge the two branches of which span the gap in the anterior marginal ridge. In the right valve the median ridge simply terminates against the ventral portion of the anterior marginal ridge. Shell surface, between the ridges, coarsely pitted, finely pitted on the ridges. Eye swelling distinct. Left valve larger than the right, overlapping it strongly in the anterodorsal region. Carapace dimorphism imperceptible. Normal pore canals of funnel type with a recessed sieve plate (Fig. 23F); setae long and flattened. Hinge holamphidont, all elements smooth, although the posterior and anterior teeth of the right valve are subdivided (Fig. 23D, E). Muscle scars have three adductor scars divided, only the most ventral scar remains single; three frontal scars of which the central scar is divided. Duplicature broad with over 50 straight marginal pore canals of which some branch (Fig. 21F); attached areas large, three in number (Fig. 18D). First antenna with first two podomeres geniculate; podomeres 3-6 fused, each having a single rather thick bristle and a second much thinner bristle. Second antenna (Fig. 23B) also has six podomeres of which the most distal four are fused. Spinneret bristle long in the male, not seen in the female. Endopodite of mandible (Fig. 235) terminating in three stout bristles projecting upwards and three downwardly projected bristles. Copulatory appendage with rather rounded, oval lappet (Fig. 231). Dimensions. Holotype: 1978: 154 $? carapace (disarticulated) LV. length

33 OSTRACODS FROM GALAPAGOS AND ECUADOR 2 Figure 20. Caudites asymmetricus. A. L. 2nd Antenna and mandible, male, 1978: 147 (x 210). B-F. 2nd Antenna; 2nd. 1st and 3rd thoracicappendages and maxilla, female, 1978: 148 (x 210). G. Copulatory organ, male, 1978: 149(x 195). H, I.MaleL.andRV., 1978: 149(~83).J,K,M. Internalview,?female LV. (x 83); enlargement offlange to show fibrous structure (x 750) and normal pore with &rayed seta ix , 1978: 151.

34 34 R. H. BATE ET AL. Figure 21. Caudites asymmetricus. A, B. Anterior and posterior hinge elements, RV. 1978: 150 (x 250). C. Normal pore canal with simple spatulate seta, 1978: 149 (X 1.1K). Cuudites crocu sp. nov. D, E. G. Muscle scars (x 310); external and internal views, RV., female holotype 1978: 154 (x 85). F. Anterior marginal pore canals, male LV., paratype 1978: 155 (x H, I. Externalviews male R. and LV., paratype 1978: 153 (x 85). J. External view, LV., female holotype 1978: 154 ( ~85).

35 OSTRACODS FROM GALAPAGOS AND ECUADOR 3 5 bigure 22. Comparison ofleftand rightvalvesofcauditessanctaecrucis (A, 1978: 159; B, 1978: 1601 and Cnudzfe~crocaiC, D, 1978: mm; height 0.38 mm. RV. length 0.74 mm; height 0.37 mm. Paratypes: 1978: carapace (disarticulated) LV. length 0.75 mm; height 0.37 mm. RV. length 0.74 mm; height 0.36 mm. 1978: carapace (disarticulated) LV. length mm; height 0.39 mm. RV. length 0.76 mm; height 0.39 mm. Remarks. Caudites croca sp. nov. is very close to C. sanctaecrucis Pokorny ( 1972), the right valves of both being indistinguishable (cf. Fig. 21E and Fig. 25E); the two species are easily separable, however, on the morphology of the left valve, that of C. sanctaecrucis being ornamented with the same ridge pattern as the right valve whereas in C. croca there is a ventrolateral crook-shaped termination of the postero-vertical ridge. The pattern of attached areas for the duplicature differs only slightly; in C. croca (Fig. 17D) there are three attached areas while in C. sanctaecrucis there are four attached areas (Pokorny, 1972: fig. 18e; Fig. 18C, herein), the upper two corresponding to the single larger dorsal area in C. croca. Thus, although the two species are separable they are considered to be very closely related. Unfortunately no copulatory appendage for C. sanctaecrucis has yet been found, and the other appendages offer no help in separating the species. The normal pore canals do, however, provide some additional evidence in support of the shell morphology (cf. Figs 23F, H, 251, K, 26C). Cauditesparanteroides Pokorny, (Fig. 24A-N) 1972 Cauditesparanteroides Pokorny: 291, figs 4h-i, 16a-d, 17, pl. 2, fig. 2a, b. Remarks. Caudites paranteroides has a more complicated ridge pattern than the other species recorded here - it also has a granular, rather than a pitted, shell surface. Two types of setae are present: simple (Fig. 24H) and with radiating spokes (Fig. 24B). The holamphidont hinge differs from that of other Caudites species in that the anterior tooth of the right valve has a subsidiary tooth projecting forwards from its base (Fig. 24K). In the left valve the selvage behind the posterior socket

36 36 R. H. BATE ET AL Figure 23. Cuudites crocu sp. nov. A, H, D-F. Internal view ( ~85) and normal pore with spatulate seta (1.05K); female LV., anterior and posterior hinge elements (~85); sieve plate normal pore and spatulate seta (x4.1k), female RV., holotype 1978: 154. B, C, G, I, J. 2nd Antenna; 3rd thoracic appendage; maxillapalp; copulatory organand mandible(x220), male paratype 1978: 153.

37 OSTRACODS FROM GALAPAGOS AND ECUADOR 37 (Fig. 245) is dentate, a feature not observed in any previously described species but seen here in a new species (p. 42) that in general morphology appears to be closely related to C. paranteroides. The spinneret bristle is long and slender in the male (specimen 1978: 1561, 1st antenna (Fig. 24G) with first two podomeres geniculate and podomeres 3-6 fused; appendage terminating in three strong, claw-like bristles. Mandible (Fig. 24M) typical of the family. Copulatory appendage (Fig. 24E) slightly deformed with bluntly rounded lappets and a ventral incurvature that, if not introduced by dissection, readily separates it from that of C. croca where there is no incurvature (Fig. 23I), and from C. asymmetricus (Fig. 20G) where there is only a shallow incurvature. Caudites paranteroides is one of the smaller species of Caudites that inhabit the waters around the Galapagos Islands. Dimensions. 1978: 1568 carapace (disarticulated) RV. length 0.57 mm; height 0.28 mm. 1978: 1579 carapace (disarticulated) LV. length 0.60 mm; height 0.32 mm. RV. length 0.60 mm; height 0.30 mm. Distribution and ecology. Found off Mosquera Islet on marine algae and recorded by Pokorny from north of Espafiola (Hood) Island and off San Salvador (James) and Santa Cruz Islands. Caudites sanctaecrucis Pokorny, (Figs 18C, 22A, B, 25A-L, 26A-G) 1972 Caudites sanctaecrucis Pokorny: 294, figs 4j, 1Od-f, 18d, e, pl. 3, fig. la, b, pl. 6, fig. la, b. Remarks. The remarkable feature of Caudites sanctaecrucis is the ornamentation of the right valve, identical to that of the right valve of C. CTOCU sp. nov., the two species being separable on the left valve as discussed previously. Caudites sanctaecrucis is, like the related C. croca, one of the larger species of Caudites living around the Galapagos Islands. Although no adult male was availablr for dissection, the -1 instar dissected turned out to be a pre-adult male on the evidence of the long spinneret bristle of the 2nd antenna (Fig. 26E); the spinneret bristle of the female (Fig. 26D) is shorter and characteristically swollen behind the joint. All thoracic appendages of the -1 instar have four podomeres, the first geniculate, and each bearing a stiff knee bristle. Mandible with seven teeth. The duplicature is very broad with a characteristic pattern of three fused areas (Fig. 18C) separated by rather wide unattached areas that contrast with the narrow unattached areas of C. croca. Muscle scars have the upper three adductors divided and the central frontal scar divided in some individuals (Fig. 25B) though not in all (Fig. 25A, H). Two types of normal pore canal setae are present: simple (Fig. 251, K) and 4- rayed (Fig. 26C); the associated apertures are either simple, funnel type or with nodes. Dimensions. 1978: carapace (disarticulated) LV. length 0.69 mm; height 0.39 mm. RV. length 0.69 mm; height 0.37 mm. 1978: 1599 RV. length 0.72 mm; height 0.38 mm. 1978: 160 Q carapace, length 0.71 mm; height 0.39 mm; width 0.26 mm. 1978: LV. length 0.74 mm; height 0.39 mm. 1978: instar (disarticulated) LV. length 0.57 mm; height 0.32 mm. RV. length037 mm; height 0.30 mm. Distribution and ecology. Recorded from Punta Suarez, Hood Island on marine algae and by Pokorny from off Santa Cruz and San Salvador (James) Islands.

38 38 R. H. BATE ET AL. Figure 24. Caitdztespurunteroides. A-D, F-H, J-N. External view, LV. (~85); normal pore with 5-rayed srta (~900); internal view, RV. ( ~85); internal view, LV. ( ~85); anterior element, LV. hinge (~250); 2nd antenna (~213); normal pore canal with simple flagellate seta (~900); posterior element, LV. hinge 1x250); anterior and posterior elements, RV. hinge (~250); mandible and 3rd thoracic appendage (~2131, female, 1978: 157. E, I. Copulatory appendage (~210) and external view, RV. (~851, male, 1978: 156.

39 OSTRACODS FROM GALAPAGOS AND ECUADOR 39 Figure 25. Caudites sanctaecruczs. A, H, I, K. External view, female RV. (~85); muscle scars (~275); papillate normal pore with flagellate seta (x600) and simple normal pore with flagellate seta (x 1. lk), 1978: 159. B, E. Leftandrightviews, femalecarapace, 1978: 160(~85). C,D,J, L. Internalviewfemale right valve (x 85); internal view female left valve ( ~85) and posterior and anterior elements of left valve hinge (x ZOO), 1978: 158. F, G. Right and LV., juvenile instar (pre-adult male), 1978: 162 (x 85).

40 40 R. H. BATE ET AL. Caudites symmetricus sp. nov. (Fig. 18B, 26H-0,27A-C) Derivation of name. From the greek symmetros, symmetrical, pertaining to the similar ornament on the left and right valves. Diagnosis. Caudites of smallish size with main medio-lateral ridge extending from postero-dorsal to anteroventral region in both valves. Anterior marginal ridge complete. Postero-vertical ridge in right valve only. Shell surface smooth except for some pitting just inside the anterior marginal ridge. Marginal pore canals numerous. Holotype. 9 carapace, : 164. San Pedro beach, Ecuador. Material. $2 carapace, 1978: 163 and juvenile instar, 1978: 224 San Pedro beach, Ecuador. Colour $species. Amber. Distribution and ecology. Only recorded from San Pedro beach on green algae. Description. Carapace small with caudal process low down, the line of greatest length passing below mid-height. Anterior margin broadly rounded; dorsal margin slightly convex in both valves; ventral margin only slightly incurved. Left valve larger than the right which it overreaches antero- and posterodorsally. Right valve with shallow concavity above eye swelling. Oblique median ridge posterodorsally upturned; in right valve only, a short, oblique posteroventral ridge joins the median ridge to produce a forked postero-vertical ridge that is lacking in the left valve. A marginal ridge extends along the dorsal margin and around the anterior margin to die out at the ventral incurvature. Shell surface smooth except for some pitting that may be present posterior to the anterior marginal ridge. Normal pore canals have two types of projecting setae (Fig. 27C): the first (4-rayed type) has four radiating spokes and projects from a small, simple aperture; the second projects from a larger aperture having a raised rim and is a much longer seta with long lateral branches and a terminal fork (fish-tail type). Hinge holamphidont ; muscle scars not seen. Duplicature broad with three oval, laterally elongate attached areas (Fig. 18B); marginal pore canals straight, short and numerous (over 40). First antenna composed of six podomeres, the first two large, distal four smaller, each having a stout bristle at its distal end. Podomeres 4 and 5 fused. Second antenna also having six podomeres with 3-6 fused. Spinneret bristle of female short. Mandible with six teeth. Thoracic appendages with knee bristle, four podomeres and a terminal claw. Dimensions. Holotype, 1978: 164, 9 carapace, length 0.50 mm; height 0.26 mm; width 0.21 mm. Paratypes: 1978: carapace (disarticulated) LV. length 0.49 mm; height 0.27 mm. RV. length 0.50 mm; height 0.26 mm. 1978: 224, juvenile carapace, length 0.37 mm; height 0.20 mm; width 0.15 mm. Remarks. Caudites symmetricus sp. nov. has a similar rib pattern on both valves, except for the postero-vertical ridge, and in dorsal view the carapace has a symmetrical appearance. This species is smaller than C. asymmetricus and although both have a diagonal ridge this occurs only in the right valve of C. asymmetricus. The unusual construction of the flange in C. asymmetricus is not exactly the same as occurs here, but the flange of C. symmetricus is certainly fluted and does have some similarities to that of C. asymmetricus. Caudites angulata Puri, 1960 from the West coast of Florida and C. medialis Coryell 8c Fields, 1937 from the Middle Miocene of Panama bear some morphological resemblance to C. symmetricus ; C. medialis is, however, a slightly

41 OSTRACODS FROM GALAPAGOS AND ECUADOR Figure 26. Caudites sanctaecrucis. A, B. Anteriorandposteriorelements, RV. hinge, 1978: 158 (x 200). C. Normal pore with 4-rayed seta, 1978: 159 (x 1.8Kj. D, F, G. 2nd Antenna; maxilla and mandible, lemale, 1978: 158 (~250). E. 2nd Antenna, pre-adult male instar, 1978: 162 (~2731. Caudites symmetricus sp. nov. H-K. 2nd Antenna, mandible; 2nd and 3rd thoracic appendages, female, 1978: 163 (x 204). L, N, 0. Internal view, LV., external view right valve and marginal pore canals, LV., PdrdtYpC 1978: 163 [x 85). M. Right side, female carapace, holotype 1978: 164 (x 85).

42 12 R. H. BATE ET AL smaller species that may be distinguished by the anterior branching of the median ridge, while C. angulata is a slightly larger species that differs in the ornamentation of the left valve (a posterovertical ridge is present and the anterior ridge is thicker). Cauditesfragdis Le Roy, 1943 from the Plio-Pleistocene of California also has an oblique median ridge but lacks the posterovertical ridge in the right valve, and also belongs to that group of Caudites species that have an hunched-up appearance due to the concavity of the ventral margin. Caudites symmetricus has almost straight dorsal and ventral margins that slope to the posterior. Caudites tricostata sp. nov. (Figs 18A, 27D-P, 28A-F) Derivation of name. After the ornamentation of three lateral ridges in the posterior half of the carapace. Diagnosis. Small species of Caudites having three lateral ridges in posterior half of carapace: dorsolateral, mediolateral and ventrolateral, extending forwards from short postero-vertical ridge. Dorsolateral and mediolateral ridges join above and in front of central muscle scars to form single, weak ridge that extends forwards to the anteroventral margin. Oblique anterior marginal ridge in anterodorsal region. Eye swelling poorly developed. Ventral margin distinctly incurved. Short, blunt-ended caudal process. Holotype. Q carapace, 1978: 169, Punta Canoa beach, Ecuador. Material. 16 specimens from Punta Canoa and San Pedro beaches, Ecuador. Colour ofspecies. Yellowish-brown. Distribution and ecology. Punta Canoa beach and San Pedro beach, Ecuador on green algae. Description. Carapace small with strongly incurved ventral margin. Dorsal margin broadly convex in both valves; caudal process low, blunt-ended; line of greatest length below mid-height. Shallow anterodorsal concavity in right valve above rather weak eye swelling. Carapace parallel-sided in dorsal view with the left valve slightly larger than the right. Shell surface finely pitted between the ridges. Anterior marginal ridge complete, cutting back obliquely across anterodorsal region from a point at about mid-height. A short postero-vertical ridge gives rise to three lateral ridges in both valves: a dorsolateral, a mediolateral and a ventrolateral. The dorsolateral and mediolateral ridges join just above and to the front of the central muscle scar field to form a single, rather weak ridge, that continues in an anteroventral direction to join the anterior margin. Two types of setae project from the normal pore canals (Fig. 275): the first is rather large, ilattened and unbranched; the second with several branches radiating out from a central axis (multi-rayed type). Hinge holamphidont with a dentate selvage behind the posterior socket of the left valve (Fig. 28A). Muscle scars typical of the genus; duplicature broad with somewhat rounded attached areas (Fig. 18A). First antenna with six podomeres the last four of which each posses a short, stout, distal bristle. Second antenna with long, delicate spinneret bristle and two terminal claws. Mandibular palp with six teeth; endopodite as for the family, with terminal setae of moderate length. Thoracic appendages have four podomeres of which the basal podomere has a knee bristle; each leg terminates in a curved claw. Copulatory appendage (Fig. 27K) with a broad, triangular lappet. Dimensions. Holotype: 1978: 169,Q carapace, length 0.47 mm; height 0.26 mm; width 0.19 mm. Paratypes: 1978: 165 carapace (disarticulated) LV. length

43 OSTRACODS FROM GALAPAGOS AND ECUADOR 43 Figure 27. Cuudites symmetricuj sp. nov. A-C. Left and dorsal views (x 85), female carapace and normal pore canal setae (4-rayed and fish-tail) (x 1.5K), holotype 1978: 164. Cauditestricostata sp. nov. D, H, J. Left side and dorsal views, female carapace (~8.5) and normal pore canal with spatulate and multirdyedsrtaelx 1.8K), holotype 1978: 169. E. FemaleRV.,paratype 1978: 166(x85). F, G, I, K-M, 0, N. Male LV., internal views L. and RV. (~85); copulatory appendage, mandible, 2nd antenna (spinneret bristle with projecting thread) and maxilla (~237) and muscle scars (x400), male paratype 1978: 165. P, 3rdThoracicappendage, female paratype 1978: 166(~229).

44 44 R. H. BATE ET AL mm; height 0.26 mm. RV. length 0.50 mm; height 0.23 mm. 1978: carapace (disarticulated) LV. length 0.49 mm; height 0.26 mm. RV. length 0.49 mm; height 0.24 mm. 1978: LV. length 0.49 mm; height 0.24 mm. 1978: 168, Q LV. length0.47 mm; height024 mm. Remarks. Caudites tricostata sp. nov. has the same unusual dentate development of the selvage behind the posterior socket of the left valve hinge as does C. paranteroides. Caudites chipolensis Puri, 1953 from the Miocene of Florida has a comparable ornamentation of three lateral ridges but they do not join anteriorly as in C. tricostata. In addition, C. cha$olensis has a number of short transverse ribs that produce a subreticulate effect absent from C. tricostata. Genus Palaciosa Hartmann, 1959 Palaciosa cracenta sp. nov. (Figs 18E, 28G, 29A-M, 30A-H) Derivation of name. Latin cracens-entas, graceful. Diagnosis. Species of Palaciosa having faint reticulation with pitted shell surface between. Low ridge extends from eye swelling, around anterior margin and back along ventrolateral margin. Posterior end of carapace sharply delimited from caudal process giving carapace a wedge-shaped outline in dorsal view. Lappet of copulatory appendage beak-like with dorsal projection and straight ventral edge. Spinneret bristle of female 2nd antenna not excessively swollen, about twice thickness of male spinneret bristle. Holotype. Q carapace, 1978: 171, San Pedro beach, Ecuador. Material. 49 specimens from San Pedro beach, Ecuador. Colour ofspecies. Yellowish brown. Distribution and ecology. Two localities recorded so far from the coast of Ecuador on marine green algae. Description. Carapace oval-rectangular in outline with gently arched dorsal margin (more distinctly so in the female) and incurved ventral margin. Carapace wedge-shaped in dorsal view, slender-especially so in the smaller male dimorph. Shell surface with a reticulation of smooth striae separating irregularly shaped, very neatly pitted areas. Eye swelling low; low anterior marginal ridge extends down from eye swelling around anterior margin to extend back along ventrolateral border. Posterior end of carapace sharply delimited from caudal process. Normal pore canals recessed, simple and few in number, widely scattered over shell surface; setae plumose (Fig. 29H). Left valve larger than the right, overlapping in the anterodorsal region. Hinge holamphidont ; anterior tooth of right valve with small tooth projecting forwards from its base. Muscle scars with median two adductors divided and the three frontal scars undivided. Duplicature very broad anteriorly with marginal canals, some of which branch. Attached areas of duplicature produce a characteristic pattern of three broad areas (Fig. 18E) of which the uppermost is subdivided into three almost equal units; the lowermost attached area may also have a small unit split off it as suggested by the illustration but this condition has not yet been observed. First antenna has six podomeres, the distal four fused; each podomere bears a short, thick bristle. The first two podomeres are geniculate. Second antenna also with six podomeres, the last four fused and the distal podomere having three claw-like bristles. Spinneret bristle of the male long and slender; of the female, shorter and about twice as thick

45 OSTRACODS FROM GALAPAGOS AND ECUADOR Figure 28. Caudites tn'costata sp. nov. A-D. Posterior end showing dentate selvage and anterior end, LV. hinge and anterior and posterior ends, RV. hinge, male paratype 1976: 165 ( X 400). E, F. 2nd and 1st Thoracic appendage, female paratype 1976: 166 (x 229). Palaciosa macenta sp. nov. G. Left side, female carapace(now disarticulated), paratype 1978: 172 (X 85). H. Leftside, femalecarapace,paratype 1978: 176 (x 85). I, L. Anteriorandposteriormarginalporecanals(transmitted light), femaleparatype 1978: 174 8e 154. J, K, M. Anteriorandposteriorhingeelements(~325)andinternalviav(X 85),femaleRV., pdratypc 1978: 172. N. Left side, -1 instar, paratype 1978: 173 (X85).

46 4 b R. H. BATE ET AL. Figure 29. Palaciosa wacmta sp. nov. A, B, G. Posterior and anterior elements, LV. hinge ( ~325) and internal view (x85), female paratype 1978: 172. C, Muscle scars, female RV., paratype 1978: 172(x325). D, Right valve, male paratype 1978: 170 (~85). E, RV., female holotype 1978: 171 (~85). F, H. Dorsal view, female carapace ( ~8.5) and tasellate seta and normal pore (~27.51, paratype 1978: 176. I, Dorsal view, male carapace, paratype 1978: 177 (~85). j, L. Copulatory organand 1st antenna, male paratype 1978: 170 (~250). K, M. Mandible and maxilla, female paratype 1978: 172 (~250).

47 OSTRACODS FROM GALAPAGOS AND ECUADOR 41 as that of the male. All thoracic appendages have four podomeres and terminate in a strong claw-the appendages of the male are smaller than those of the female. Copulatory appendage with terminal lappet having straight ventral margin and convex dorsal outline-the dorsal edge beak-like and with a pointed projection (Fig. 295). Dimensions. Holotype: 1978 : 17 1, 9 carapace (disarticulated) LV. length 0.60 mm; height 0.30 mm: RV. length 0.60 mm; height 0.29 mm. Paratypes: 1978: carapace (disarticulated) LV. length 0.53 mm; height 0.26 mm. RV. length 0.53 mm; height 0.26 mm. 1978: 172, 9 carapace (disarticulated) LV. length 0.59 mm; height 0.30 mm: RV. length 0.59 mm; height 0.29 mm. 1978: 173, -1 instar, carapace, length 0.47 mm; height0.26 mm; width 0.17 mm. 1978; 174, 9 carapace, length 0.57 mm; height 0.29 mm; width 0.22 mm. 1978; 175, 9 RV. length 0.59 mm; height 0.30 mm. 1978: 176, 9 carapace, length 0.60 mm; height 0.30 mm; width 0.21 mm. 1978: 177, 8 carapace, length 0.55 mm; height 0.27 mm; width 0.17 mm. Remarks. Palaciosa cracenta sp. nov. is placed in Palaciosa rather than Caudites because of the absence of lateral ribbing and the presence of marked sexual dimorphism. The spinneret bristle of the female also differs from that of Caudites species by being slender in comparison. The tasellate normal pore canal setae of P. cracenta contrast with the variable types found in Caudites (see under Remarks for Caudites). The muscle scars do not, however, appear to differ from those present in Caudites which are themselves subject to variation with respect to the division of the adductor or frontal scars. The complexity of the muscle scar pattern illustrated for Palaciosa by Hartmann (1959: pl. 45, fig. 156) and by Pokorny (1972: 273) is not that great when the dorsal muscle scar pattern is removed from the adductor/frontal scar assemblage and, indeed, is basically concerned solely with the inclusion of an additional adductor scar that may or may not be observable due to preservation. Palaciosa vandenboldi Hartmann, 1959, the type-species from El Salvador, differs from P. cracenta by having a smooth shell, a different pattern of attached areas for the duplicature, slightly fewer marginal pore canals and a copulatory appendage in which the lappets terminate in a rather blunt end as opposed to the rather pointed termination in P. cracenta. Palaciosa sp. A and sp. B from the Holocene of North America (Valentine, 1976) differ both in outline and in the smoothness of the shell surface. P. sp. B also has some ribbing that additionally contrasts it with P. cracenta. Family Loxoconchidae Sars, 1925 Genus Touroconcha Ishizaki & Gunther, 1976 Remarks. The features of Touroconcha that set it apart from Loxoconcha concern the carapace shape: the posterior being virtually caudate and developed above midheight and contrasting with the more broadly rounded posterior of Loxoconcha. Additionally the dorsal outline of Touroconcha is not arched as in Loxoconcha and the hinge is, therefore, straight. The turreted sieve-plate pore canals are also characteristic of this genus. The hinge is gongylodont but shows some slight modification in some species when the posterior element of the left valve consists ofa socket and tooth only rather than a socket- tooth-socket arrangement.

48 48 R. H. BATE ET AL. Touroconcha lapidiscola (Hartmann, 1959) (Figs301-0,31G,H, 32A) 1959 Loxoconcha lapidiscola Hartmann: 223-4, pl. 41, figs 128-9, pl. 42, figs Not 1963b Loxoconcha lapidiscola Hartmann; van den Bold: 394, pl. 8, fig Loxoconcha lapidiscola Hartmann; van den Bold: 51, pl. 4, fig. 8a,b. Not 1969 Loxoconcha lapidiscola Hartmann; Swain: 469, pl. 6, fig. 6a,b, pl. 11, fig Loxoconcha? lapidiscola Hartmann; Swain 8c Gilby: 324, fig. 24, pl. 5, fig. 9a,b. Not 1976 Touroconcha lapidiscola (Hartmann); Ishizaki & Gunther: 20, pl. 9, figs Emended Diagnosis. Ornate species of Touroconcha in which posteroventral triangulation has an incurved ventral boundary. Posterior reticulum not subdivided. Remarks. Touroconcha lapidiscola was first described by Hartmann from the Gulf of Fonseca, El Salvador, and his illustration (pl. 42, fig. 13 1) shows the posteroventral triangulation that is indented on its lower boundary (see Figs 3OI,J,O,N). This feature is diagnostic of the species lapidiscola and is used here to distinguish between the closely related species that are present on the Pacific seaboard of Central and South America and around the Galapagos Islands. Swain 8c Gilby ( 1974) record this species from San Juan del Sur Bay, Nicaragua while van den Bold (1966) records it from Colon Harbour, Panama and (1977) from Costa Rica, Venezuela and the Antilles. The record by van den Bold ( 1963b) of lapidiscola from the Upper Miocene, Spring Vale Formation of Trinidad is considered to be of a closely related species only; the absence of the posteroventral indentation of the ornament prevents it from being conspecific. This is true also for Ishizaki 8c Gunter s record of the species from the Gulf of Panama. It is considered that van den Bold s Miocene species is an ancestral form that gave rise to lapidiscola and to Ishizaki 8c Gunther s species. Touroconcha lapidiscola has not been recorded south of Ecuador or further west than Clipperton Island. It seems likely therefore, that its Pacific distribution is limited mainly to the Central America region down to Ecuador and the Galapagos Islands. Dimensions. 1978: LV. length 0.54 mm; height 0.30 mm. 1978: 203 Q LV. length 0.48mm; height 0.28mm. 1978: LV. length 0.45mm; height mm. 1978: RV. length0.46 mm; height0.27 mm. Distribution and ecology. From Punta Suarez, Hood Island and Mosquera Islet on marine algae and from San Pedro beach, Ecuador on green algae. Previously recorded from off El Salvador (Hartmann, 1959), Nicaragua (Swain 8c Gilby, 1974) from Colon Harbour, Panama (van den Bold, 1966) and from Costa Rica, Venezuela and the Lesser Antilles (van den Bold, Touroconcha mosqueraensis sp. nov. (Figs 31A-F, I-N, 32D, 33A) Deriuation ofname. After the type and, so far, only locality, Mosquera Islet. Diagnosis. Touroconcha having coarsely reticulate shell ornamentation in which the posteroventral triangulation is composed of three straight sides; posterior

49 OSTRACODS FROM GALAPAGOS AND ECUADOR 49 Figure 30. Palaciosa cracenta sp. nov. A, C, F, G. lst, 2nd and 3rd Thoracic appendages and 2nd antenna, male paratype 1978: 170 (~250). B, D, E, H. lst, 2nd and 3rd Thoracicappendages and 2nd antenna, female paratype 1978: 172 (~250). Touroconcha lapidiscola. I, K, L, M. External view (x105) female RV. ; posterior hinge element (~300); internal view (X 105) and anterior hinge element (~3001, 1978: 205 Galapagos specimen. J, 0. External view, female LV. (X 105) and enlargement of posteroventral ornament (x 148), 1978: 203 Galapagos specimen. N. Externalview, malelv., 1978: 202 from Ecuador(x 105).

50 50 R. H. BATE ET AL. reticulum subdivided to have vertical row of three chambers at the back and low secondary reticulation at the front. Holotype. 1978: carapace, Mosquera Islet. Material. 1978: LV. Mosquera Islet. Distribution and ecology. Only recorded from Mosquera Islet on marine algae. Description. Carapace rectangular, typically loxoconchid in shape in male dimorph; female not seen. Shell coarsely ornamented by upraised ridges that form a diagnostic pattern identical in both left and right valves (Fig. 3 IA,B). Secondary reticulation present within the primary reticulum. Normal pore canals of two types: upraised canals clearly visible in lateral view and having a recessed sieveplate surrounded by a raised rim; the sieve-plate has a central setal pore (Fig. 33A). The second type of normal pore canal aperture is also of the sieve-plate type but this is not recessed, the plate being clearly visible and with an off-centre setal pore (Fig. 33A). Eye node distinct with five ridges radiating from it; internally represented by a deep ocular pit situated below the anterior hinge element. Hinge gongylodont with smooth terminal elements and coarsely dentate/loculate rnedian element. Duplicature broad anteriorly and posteroventrally. No more than ten long, straight, anterior marginal pore canals. A distinct flange extends around the anterior margin and along the posteroventral margin to die out at the anteroventral incurvature. Muscle scars poorly preserved but four oval adductor scars with an oval (?) frontal scar situated slightly above an antero-central position have been observed. First antenna slender, six-jointed, although podomeres 4 and 5 are fused; last podomere has two long setae, penultimate podomere has four long setae. Second antenna geniculate, more powerfully developed than 1st antenna; five-jointed (podomeres 4 and 5 fused) and with two terminal claws. Spinneret bristle reaches to the end of the last podomere. Mandible with six teeth and endopodite with three curved ventral setae and three, slightly more powerful, curved terminal setae. Maxilla with three masticating lobes terminating in short bristles and a slightly larger palp ; vibratory plate with 14 setae. Thoracic appendages not preserved. Dimensions. Holotype: 1978 : 200 carapace (disarticulated) LV. length 0.55 mm; height 0.29 mm. RV. length 0.55 mm; height 0.29 mm. Paratype: : LV. (originally a carapace but RV destroyed during dissection) length 0.55 mm; height0.30 mm. Remarks. Only two specimens, both males, have been found of this species but they are sufficiently distinct to be recognisable as new. Ornamentally Touroconcha mosquerumis sp. nov. has a basic reticulate pattern of ridges strikingly similar to that of T. lapidiscola (Hartmann) (cf. Figs 301,N with 3 la,b) but differing by having a greater development of secondary reticulation, less prominent reticulum and by having the triangular reticulum in the postero-ventrolateral region bounded by three straight sides without the ventral indentation of T. lapidiscola. The large, posterolateral hexagonal reticulum in T. mosqueraensis is divided by a vertical ridge with three reticula behind it (Fig. 3 la,b); in T. lapidiscola the hexagonal reticulum is only incompletely divided and lacks this internal reticulation (Fig. 30J-L). Touroconcha lapidiscola of Ishizaki 8c Gunther (1976) differs from the true lapidiscola in the posteroventral region (lacking the triangulation with incurved lower side) and from both lapidiscola and mosgueraensis in the development of the posterior reticulum. Indeed Ishizaki 8c Gunther s specimens have a posterior reticulum that extends over the whole of the posterior third of the valve and this must be a new

51 OSTRACODS FROM GALAPAGOS AND ECUADOR 5 1 Figure 31. Tourocmchu mosquerd sp. nov. male holotype 1978: 200. A-D. External and internal views, R and LV. (x 105). E, F. Anterior and posterior ends, RV. hinge (~350). I, J. Posterior and anterior ends, LV. hinge (~350). K-N. 2nd Antenna; 1st antenna; mandible and maxilla (~218). Touroconchalapzdzscola. G, H. Posterior and anterior ends, female LV. hinge, 1978: 204 (~375).

52 !i 2 R. H. BATE ET AL Figure 32. Variation in ornamentation between species of Touroconcha. Important areas used in taxononiy shaded. A, T. lapidiscola. B, T. sp. (figd Bold, 1963b as T. lapidiscola). C, T. sp. (figd Ishizaki & Gunther, 1976 as T. lapidiscola). D, T. mosqueramis sp. nov. species of the genus. The fossil lapidiscola ofvan den Bold ( ) appears to lack a posterior reticulum as developed in the species mentioned above while the elongate reticulum that is present in all species of Touroconcha in an anteroceritral position, extends back into the posterior half of the carapace. The possible relationship of all these forms, developed from the Upper Miocene ancestor in the Caribbean, will be dealt with in a later section. Genus Loxoconcha Sars, 1866 Subgenus Loxoconcha Sars, 1866 Loxoconcha (Loxoconcha) sp. A (Fig. 33B-D) Remarks. A single carapace, possibly a -1 instar, having a finely reticulate ornamentation the ridges of which have a granular appearance. The reticulation becomes somewhat coarser at the anterior and posterior ends. The unique feature of this specimen is the ribbing along the posteroventral margin that sets it apart from all others recorded from the Pacific seaboard of the Americas. Of the appendages, only the antennae and maxilla have been preserved. The 1st antenna is long and slender, terminating in three long setae. The 2nd antenna has an unusually long 5th podomere and a well developed spinneret bristle (Fig. 32C), much longer than that present in T. lapidiscola or T. mosqueraensis. Dimensions : 206 carapace (disarticulated and LV destroyed) RV. length 0.38 mm; height 0.23 mm. Distribution and ecology. San Pedro Beach, Ecuador on green algae. Subgenus Loxocorniculum Benson & Coleman, 1963 Remarks. Loxocorniculum was introduced by Benson 8c Coleman (1963) for loxoconchid species having a reticulate ornamentation and, more important, a horn-like posterodorsal protuberance. Since its introduction the genus has been expanded to include pitted forms although many authors still place these in Loxoconcha. Two species recorded here from the Galapagos, both pitted, have a prominent posterodorsal projection. One of us (J.E.W.) would prefer to retain these in Loxoconcha, recognising the species as belonging to the rhomboidea group

53 OSTRACODS FROM GALAPAGOS AND ECUADOR with respect to carapace outline and copulatory appendage. The other author (R.H.B.) considers that the genetic control that must exist, for so many species to have this posterodorsal projection, indicates a degree of relationship between the species sufficient to set them apart from other loxoconchids. At the same time, however, the distinction between species having a posterodorsal projection and those that do not is not always clear; because of this a subgeneric category is maintained here. Loxoconcha (Loxocorniculum) lenticuloides (Swain 8c Gilby, ) (Figs 34B,M, 35A-K, 36A,B) 1974 Loxocorniculum lenticuloides Swain& Gilby: 325, pl. 5, fig. 7. Remarks. Loxoconcha (Loxocorniculum) lenticuloides was recorded from off Nicaragua by Swain & Gilby and here from Ecuador and the Galapagos Islands. It is thus one of the few species occurring off the coast of mainland South America that has been able to make the journey to the Galapagos Islands. Loxoconcha (L.) lenticuloides belongs to a group of related species that have L. (L.) purisubrhomboidea from the Pliocene of N. Carolina as their ancestor. Other species in this group are L. (L.) matagordensis Swain, 1955 and a new species from the Galapagos Islands that appears to have evolved directly from it, L. (L.) occidentale (see below). Swain 8c Gilby in their description of Loxocorniculum lenticuloides state that it is weakly pitted to nearly smooth marginally. Their figure (pl. 5, fig. 71, however, shows distinct pitting right up to the anterior and posteroventral margins - a feature that our material exhibits particularly well (Figs 35A,B, 36A). Loxoconcha (Loxocorniculum) lenticuloides may be contrasted with L. (L.) matagordensis by having a larger number of pits; less positively developed anterior marginal ridges (especially true in the male) ; a more strongly developed posterodorsal projection and an anterior marginal extension of the carapace, particularly noticeable in dorsal view (Fig. 36B). Dimensions. 1978: 2078 carapace (disarticulated) LV. length mm; height 0.30 mm. RV. length 0.51 mm; height 0.30 mm. 1978: 208 juv. LV. length 0.41 mm; height 0.25 mm. 1978: carapace, length 0.64 mm; height 0.37 mm; width 0.26 mm. 1980: 79 9 carapace length 0.55 mm; height 0.37 mm; width 0.26 mm. Distribution and ecology. Punta Canoa beach, Ecuador, on green algae and from the following Galapagos localities : Hood Island, Mosquera Islet and Fernandina Island, all on marine algae. Loxoconcha (Loxocorniculum) occidentale sp. nov. (Figs 33E-M, 34A, C-L) Derivation of name. Latin, occidentalis, of the west. Diagnosis. Species of Loxocorniculum having coarsely pitted lateral shell surface, well developed anterior marginal ribbing with distinct concavity lying between ribbing and eye node, particularly well seen in dorsal view. Posteroventral border broadly and evenly convex. Holotype. 8 left valve, : 209, Mosquera Islet on marine algae. Material. 62 specimens from Mosquera Islet, Punta Suarez, Hood Island and Fernandina Island. Colour $species. Grey. is

54 R. H. BATE ET AL. Figure 33. Touroconcha mosperaensis sp. nov. A. Normal pore canals and sieve plates, LV. holotype 1978: 200 (~500). Loxoconcha (Loxoconcha) sp.a. B, C, D. RV. (x 105); 2nd antenna and 1st antenna 1978: 206 (~206). Loxoconcha (Loxocorniculwn) occidentale sp. nov. E, L, M. Internal view (~83); posterior and anteriorhingeelernents(x 350)femaleLV., paratype 1978: 214. F, FemaleLV.,paratype 1978: 211 (x 83). G. Male LV., paratype 1978: 209 (x 83). H. Elongate sieve normal pore with seta, temale paratype 1978: 221 (x 1.4K). I. Female RV., paratype 1978: 212 (X 83). J. Male RV., paratype 1978: 210 ( ~83). K. Dorsal view, female paratype 1978: 221 ( ~83).

55 OSTRACODS FROM GALAPAGOS AND ECUADOR 55 Distribution and ecology. Most abundant in the fauna collected from Mosquera Islet but present in the other two localities sampled from the Galapagos Islands - occurs on marine algae. Description. Carapace oval-quadrate in the female dimorph with convex dorsal margin, broadly convex posteroventral border and rounded anterior margin; the line of greatest length extending through midpoint. Anterodorsal margin long and very slightly concave. Male dimorph similar though more rectangular in shape. Eye node distinct; posterodorsal node well developed. Shell surface coarsely pitted with the pits less dense at valve centre; pits decrease in size towards the valve margins. Anterior and posterior parts of shell with weak reticulation superimposed - the reticula extending forwards anteriorly as faint ridges. Between anterior reticulation and eye node a broad, shallow concavity is developed, particularly well seen in dorsal view (Fig. 33K). Normal pores with either round (Fig. 34E) or elongate (Fig. 33H) sieve plates depending on position on the shell. Hinge gongylodont. Muscle scars with four elongate adductor scars and crescentic frontal scar; two small anteroventral mandibular scars (Fig. 34D). Duplicature broad anteriorly and posteroventrally, without a vestibule and with a few, straight, widely spaced marginal canals; seven anteriorly. First antenna long and slender, with five podomeres, podomeres 3 and 4 fused - four long terminal setae, penultimate podomere with four long distal setae (only three are visible in Fig. 34K). Second antenna with four podomeres in the endopodite of which the last three are fused; spinneret bristle long. Mandible and maxilla as illustrated. Copulatory appendage slightly distorted but boot-shaped (Fig. 34L), a type found in European Loxoconcha species of the rhomboidea group. Dimensions. Holotype: 1978: LV. length 0.61 mm; height 0.34 mm. Paratypes: 1978: RV. length 0.64 mm; height 0.37 mm. 1978: LV. length 0.54 mm; height 0.35 mm. 1978: RV. length 0.54 mm; height 0.34 mm. 1978: 213 d carapacelength0.62 mm; height0.37 mm; width0.28 mm. 1978: LV. length 0.53 mm; height 0.35 mm. 1978: LV. length 0.64 mm; height 0.36 mm. 1978: carapace (disarticulated) LV. length 0.63 mm; height 0.35 mm: RV. length 0.63 mm; height 0.35 mm. 1978: carapace (disarticulated) LV. length 0.63 mm; height 0.37 mm: RV. length 0.63 mm; height 0.36 mm. 1978: carapace (disarticulated) LV. length 0.53 mm; height 0.34 mm: RV. length 0.52 mm; height 0.32 mm. 1978: carapace length 0.55 mm; height 0.36 mm; width 0.26 mm. Remarks. Loxoconcha (L.) occidentale sp. nov. is considered to belong to the group of loxoconchids that originated in the Pliocene of N. Carolina with L. purisubrhomboidea Edwards, and from which evolved the present day group of species that inhabit the USA Atlantic and Gulf Coast: e.g. L. (L.) lenticuloides, L. (L.) matagordensis, and 2. purisubrhomboidea. The Recent forms associated with L. (L.) matagordensis and assigned by workers to L. (L.) purisubrhomboidea are considered here to belong to L. (L.) matagordensis, separation of the two into distinct species being untenable, cf. Fig. 35L (L. matagordensis) and Fig. 35M (L. purisubrhomboidea). L. (L.) occidentale from the Galapagos is close to L. (L.) matagordensis (cf. Figs 335, 35L) but, apart from having a more prominent posterodorsal node, L. (L.) occidentale differs by having a pinched-in region anterior to and below the eye swelling (Figs 33K, 34E) and a broadly and uniformly convex posteroventral margin that lacks the almost midventral downward projection of the margin seen in L. (L.) matagordensis (Fig. 35L). Nevertheless, it is considered that L. (L.)

56 R. H. BATE ET AL Figure 34. Loxoconcha (Loxocorniculum) occidentale sp. nov. A, D. Internal view ( ~83) and muscle scars (~3.501, male LV., paratype 1978: 215. C. Sieve plate normal pore with seta, female RV., paratype 1978: 212 (x 1.4K). E. Dorsal view, male carapace, paratype 1978: 213 ( ~83). F-K. 2nd Antenna; 2nd thoracic appendage; 3rd thoracic appendage; mandible; maxillary palp with masticatory processes and 1st antenna; male carapace, paratype 1978: 21 7 (~260). L. Copulatory appendage, male paratype 1978: 216 (x 163). Loxoconcha (Loxocorniculum) lenticuloides Swain & Gilby. B. Internal view, male RV., 1978: 207 (x83).m.juvenilelv.,paratype 1978: 208(x100).

57 OSTRACODS FROM GALAPAGOS AND ECUADOR 57 occidentale could have evolved directly from L (L.) matagordensis prior to its migration to the Galapagos. The similarity of L. (L.) occidentale to L. (L.) lenticuloides is only apparent in lateral view (although males of the latter lack the anterior ribbing of L. (L.) occidentale) as in dorsal view the two species are readily distinguishable (Figs 33K, 36B). Family Xestoleberididae Sars, 1928 Genus Xestoleberis Sars, 1866 Emended diagnosis. Carapace smooth, granular or pitted, sometimes with weak ridges in ventrolateral region; subreniform to subtriangular in side view, without posteroventral projection. Dimorphic, female more strongly inflated posteriorly; male tapering slightly towards posterior. Crescent-shaped groove usually present behind ocular pit. Normal pores may be of simple funnel or of sieve type. Marginal (radial) pore canals straight or branching. Anterior and posterior vestibules well developed. Hinge either paraperatodont or of artioperatodont type. Muscle scars with V-shaped or cloverleaf-shaped frontal scar. Male copulatory organs usually with asymmetrical lappets. Second antenna with two strong terminal claws. Remarks. The carapace outline, marginal pore canals and the shape of the copulatory appendage lappets are all characters that have been shown, in the past, to be important in determining species ofxestoleberis. In the Galapagos material we have noticed that in some species the terminal claws of the male 2nd antenna differ from those of the female and in these species the nature of the claws may be used as a specific character. With respect to the mandible there is also a difference between species in the number and type of teeth present, characters that have been incorporated into the description of the six Xestoleberis species recorded here. Athersuch ( 1976) comments that for his Mediterranean species the Xestoleberis spot carries internally two equal-sized, rimmed slits; here, when seen, there appears to be only a single, large rimmed slit (Fig. 44A). The Xestoleberis hinge is essentially the same as found in members of the Cytheruridae and as a consequence the terminology introduced by Bate ( : 45) is used here. Xestoleberis bellornata sp. nov. (Figs 36C-J, 37A-J, 44A) Deriuation of name. Latin, bellus, beautiful + ornatus, decorated. Diagnosis. Xestoleberis with granular shell surface in antero- and posteroventral regions, elsewhere coarsely pitted with three longitudinal ridges ventrolaterally. Surface pitting absent from young instars. Sieve plates with central setal pore and three rows of sieve pores; small simple funnel pores with large aperture. Marginal canals short and branching, more than 29 anteriorly. Second antenna with two simple, curved, terminal claws ofwhich the outer is slightly larger than inner. Holotype. 8 carapace, 1979: 16 1, San Pedro Beach, Ecuador on green algae. Material. 13 specimens from San Pedro Beach, Ecuador. Colour $species. White Distribution and ecology. Only recorded from San Pedro Beach where it occurs on marine green algae. Description. Carapace subreniform with broadly arched dorsal margin and, in the female, broadly rounded posterior; smaller male dimorph more narrowly rounded. Ventral margin distinctly incurved in the right valve, slightly less so in the

58 58 R. H. BATE ET AL. Figure 35. Loxoconcha (Loxocomiculum) lenticuloides Swain & Gilby. A-K. Male carapace, 1978: 207. A. R.V. (x 100). B. LV. (x 100). C, D. Anterior and posterior hinge elements, right valve (~350). E. Sieve plate with seta (x 1.4K). F. Internal view, LV. (x 100). G. Muscle scars from exterior (~ H-K. 2nd Antenna; mandible; 2nd thoracic appendage and 1st antenna (x 240). Loxoconcha (Loxocomzculum) matagordensis Swain. L. Male RV., 1980: 78, Recent, Texas, (~83). M. Male right valve of L. purisubrhomboidea 1979: 433, Recent, Texas (~83).

59 OSTRACODS FROM GALAPAGOS AND ECUADOR 59 left. Normal pore apertures of simple, funnel type (Fig. 361) and of sieve type (Fig. 365) in which there are three rows of sieve pores with a larger, central setal pore. Shell surface coarsely pitted except anteroventrally and posteroventrally, in which region the pits are replaced by a coarse, granular ornamentation (Fig. 36H). In - 1 instars the lateral surface is only intermittently pitted, while younger instars are devoid of pits altogether, having only the terminal granular ornament. Ventrolateral surface has two to three rather broad, shallow ridges. Normal pore canal apertures of funnel type (Fig. 361) or sieve type (Fig. 365). Hinge paraperatodont. Inner margin and line of concrescence do not coincide everywhere and a broad anteroventral vestibulum and a narrow posteroventral vestibulum result. Anterior marginal canals mainly branching, though some may be simple (Fig. 44A). Muscle scars not observed. Left valve overlaps right along anterodorsal margin and at the posterior end. Eye spot of dark, clear calcite, showing up against the opaque white shell of the carapace. First antenna with six podomeres, the second endopodite podomere bearing two outer and one inner distal setae. Second antenna with all except the first endopodite podomere fused, last podomere bearing two long smooth claws, spinneret bristle long. Maxillary palp bearing four setae on the penultimate podomere. Mandible with four strong teeth; thoracic appendages with strong claws on the 1st and 2nd legs, 3rd leg rather poorly developed - possibly damaged. Copulatory appendage with asymmetrical beak-like lappets. Dimensions. Holotype: 1979: 16 1 d carapace (disarticulated) LV. length 0.37 mm; height 0.21 mm. RV. length 0.37 mm; height 0.22 mm. Paratypes: 1979: instar LV. length 0.36 mm; height 0.19 mm. RV. length 0.34 mm; height 0.19 mm. 1979: 163 Q carapace LV. length 0.43 mm; height 0.26 mm. RV. length 0.43 mm; height 0.26 mm. 1979: 164 Q carapace LV. length 0.46 mm; height 0.27 mm. RV. length 0.43 mm; height 0.27 mm. 1979: LV. length 0.38 mm; height 0.21 mm. 1979: 166 Q RV. length 0.41 mm; height 0.26 mm. Remarks. Xestoleberis bellornata sp. nov. is easily recognisable from other species of the genus by the possession of a distinct surface ornamentation of pits associated with terminal granules. The copulatory appendage exhibits the normal asymmetry of the genus but the shape of the lappets is quite distinctive. Xestoleberis sp. 3 of Teeter (1975) has a similar carapace outline but is a smooth species that cannot be confused with the present form. Xestoleberis deforma sp. nov. (Figs 36K-M, 37K-Q 44D) Derivation of name. Latin deformis, misshapen, ugly. Diagnosis. Xestoleberis having elongate carapace with irregular dorsal outline. 2nd Antenna having serrated terminal claws, copulatory appendage with almost symmetrical beak-shaped lappets. Sieve plates with five concentric rows of sieve pores and central setal pore. Holotype. carapace, 1979: 167, Punta Suarez, Hood Island onmarinealgae. Material. -1 instar 1979: 168, Punta Suarez. Colour $species. White. Distribution and ecology. Only from the type locality. Description. Carapace elongate with well rounded ends ; dorsal margin slightly convex with cardinal angles projecting; ventral margin incurved. Shell surface

60 60 R. H. BATE ET AL Figure 36. Loxoconcha (Loxoconiculum) lenticuloides Swain & Gilby. A, B. Right side and dorsal views, female carapace, 1980: 79 (~83). Xestoleberis bellonata sp. nov. C, D, H-J. Right and leftviews, female carapace (x 115); enlarged anterior ornament (~375); simple funnel pore and sieve plate (x3k); paratype 1979: 164. E. Male LV., holotype 1979: 161 (~115). F. Juvenile RV., paratype 1979: 162 (x 115). G. LV., -1 instar, paratype 1979: 163 (x 115). Xestoleberis de/onna sp. nov. K-M. LV., external lateral view (x 115); simple normal pore (x 1.2K) and sieve plate with seta (x 2.5K), male holotype 1979: 167.

61 OSTRACODS FROM GALAPAGOS AND ECUADOR smooth with a crumpled appearance anteriorly. Sieve plates large (Fig. 36M) having five concentric rows of sieve pores and a central setal pore. Smaller simple normal pores with a rim surrounding the setal aperture also present. Hinge paraperatodont. Muscle scars poorly seen, the frontal scar apparently rounded. Line of concrescence and inner margin not always coincident, an anterior and a posterior vestibulum developed. Marginal pore canals short and straight (Fig. 44D). Greatest length of carapace through midpoint, greatest height and width in posterior half. Left valve larger than right. First antenna six-jointed, the second podornere of the endopodite bearing a single distal seta, terminal podomere bearing two setae; setae of penultimate podomere almost as long as terminal setae. 2nd antenna massive with middle podomeres fused; terminal claws short with serrated outer edge. Mandible with six prominent teeth. Thoracic appendages rather thick-set, Copulatory appendage with almost symmetrical beak-shaped lappets. Dimensions. Holotype: 1979: carapace (disarticulated) LV. length 0.47 rnm; height 0.23 mm. RV. length 0.45 mm; height 0.23 mm. Paratype: 1979: instarlv.length0.41 mm; height0.21 mm. Remarks. This species is unique among Xestoleberis species in having an unusual elongate outline. From the species described here it differs in the shape of the copulatory appendage lappets and the serrated terminal claws of the 2nd antenna. hl Xestoleberis homotruncula sp. nov. (Figs 38A-P, 44E) Derivation ofname. Greek homos, uniform ; Latin trunculus, end, extremity. Diagnosis. Xestoleberis with almost equally broad anterior and posterior ends; dorsal outline arched, venter incurved. Sieve plates with off-centre setal pore and three to five rows of sieve pores; plates flat or funnel-shaped. Anterior marginal canals short, straight and numerous. Terminal claws of male 2nd antenna unequal: one long, smooth; second short with bristles; of equal length in the female. Copulatory appendage lappets distinctly asymmetrical. Holotype. 8 (carapace destroyed) 1979: 170, Punta Espinosa, Fernandina Island. Material. 13 specimens from Punta Espinosa, Punta Suarez and Mosquera Islet. Colour ofspecies. White. Distribution and ecology. As above, on marine algae. Description. Carapace reniform with broadly rounded anterior and posterior ends. Dorsal margin arched, venter incurved. Shell surface smooth with large sieve plates scattered over the surface: sieve plates with slightly off centre setal pore having five rows of sieve pores on one side and three rows on the other. Some sieve plates are funnel-shaped having concentric ridges separating the rows of sieve pores. Hinge paraperatodont. Muscle scars with a V-shaped anterocentral frontal scar, a small oval mandibular scar below this with a second oval scar beneath the adductor scars (Fig. 38E). Duplicature broad anteriorly, the inner margin and line of concrescence not coinciding and a broad anterior vestibule results; anterior marginal canals long and thin, alternating with short, thick canals that terminate blindly (Fig. 44E). First antenna thick-set with six endopodite podomeres and short, thick setae. Second antenna strongly developed with distal two podomeres fused; terminal claws of the male unequal with one long and slender, the other short and bearing 15 bristles; equal in length in the female. Mandible bearing six

62 62 R. H. BATE ET AL Figure 37.Xestoleberis bellomata sp. nov. A. 2nd Antenna, female paratype 1979: 163 (~227). B, D, F-J. Mandible; maxilla; Ist, 2nd thoracic legs; copulatory appendage showing asymmetrical lappets and 3rd thoracic appendage, male holotype 1979: 161 (~2.50). C, E. Mandible and 1st antenna, female Daratwe 1979: 162 (~265). Xestoleberis deform SD. nov. K. 1st Antenna. L. 2nd Antenna. M. 1st 1 /I Thoracic appendage. N, 0. Copulatory appendages. P. Mandible. Q. Maxilla, male holotype 1979: 167(x245).

63 OSTRACODS FROM GALAPAGOS AND ECUADOR 63 to seven teeth. Thoracic appendages with thick distal seta on 2nd podomere. Copulatory appendage with asymmetrical lappets - the right broad and triangular, the left small and narrow. Dimensions. Paratypes: 1979: 1699 carapace, length 0.49 mm; height 0.27 mm; width 0.25 mm. 1979: LV. length 0.48 mm; height 0.27 mm. 1979: LV. length 0.38 mm; height 0.24mm. 1979: carapace, LV. length 0.38 mm; height 0.22 mm. RV. length 0.37 mm; height 0.21 mm. 1979: RV. length 0.39 mm; height 0.23 mm. 1979: LV. length 0.41 mm; height 0.24 mm. Remarks. Xestoleberis homotruncula sp. nov. differs from other species of the genus in its carapace shape, in which the anterior and posterior ends are almost equally broadly rounded. The species is also distinguished by its appendage anatomy, especially the terminal claws of the male 2nd antenna and the lappets of the copulatory appendage. Xestoleberis claroculata sp. nov. (Figs 39A-J, 40A-M, 41A,B, 44G,H) Derivation ofname. Latin, clarus, bright, clear + oculus, eye. Diagnosis. Xestoleberis with flattened venter ornamented by weak longitudinal ridges and posteriorly covered by fine hairs. Dorsal margin angular. Shell surface coarsely pitted. Hinge artioperatodont. Sieve plates small with two rows of sieve pores. Simple funnel pores on lateral surface, on venter with rimmed apertures. Mandible with seven teeth; terminal claws of 2nd antenna curved, smooth. Copulatory appendage lappets billhook-shaped, the lett elongate. Nolotype. 8 carapace, 1979: 18 1, Punta Suarez, Hood Island on marine algae. Material. 23 specimens from Punta Suarez and Punta Espinosa, Fernandina Island. Colour ofspecies. White with clear, dark, eye-spot; mother-of-pearl colour when wet. Distribution and ecology. From Punta Suarez and Punta Espinosa on marine algae. Description. Carapace ovoid with angled dorsal margin: cardinal angles distinct, venter flattened. Anterior and posterior ends narrowly rounded. Shell surface strongly pitted, the pits of two sizes. Ventral and ventrolateral surfaces ornamented by weak longitudinal ridges. Posterior half ofventer covered by a mat of fine hairs, the hairs distinct from the sensory setae that project either from simple rimmed apertures on the ventral surface, or from smooth funnel pores and sieve plates on the lateral surface. Sieve plates small with two concentric rows of sieve pores. Left valve slightly larger than the right, with the greatest length of the carapace below midpoint; the greatest height anterior to midpoint and the greatest width through or slightly behind midpoint. Hinge artioperatodont. A crescentic Xestoleberis spot with single slit is situated below the eye spot (Fig. 44G). Muscle scars with a V-shaped anterocentral frontal scar. Duplicature broadest at extreme anterior; inner margin and line of concrescence do not coincide and a deep anterior vestibule is present. Anterior marginal canals very few in number, possibly about 10, short, straight and widely spaced (Fig. 44H). First antenna long, moderately slender with six podomeres. Second antenna with middle podomeres fused and two curved, smooth, terminal claws identically developed in both dimorphs. Terminal podomere with very thick distal seta that gives the appearance

64 64 R. H. BATE ET AL. Figure 38. Xestoleberis homtruncula sp. nov. A, C, E. External and internal views (x 115) and muscle scars (~3,501. right valv~ -1 instar, paratype 1979: , D, F, G. Left and RV. (x 115) and sieve plates (x4.8k),-1 instar, paratype 1979: 173. H-P. 1st and 2nd Antennae; mandible; thoracicappendages; copulatoryappendage (left and right) and maxilla, male holotype 1979: 170 (~300).

65 OSTRACODS FROM GALAPAGOS AND ECUADOR 0 5 of three terminal claws. Vibratory plate of maxilla with setae; palp bearing three coarse setae as well as four terminal setae; each process also bears four terminal setae. Mandible with seven strong teeth. Thoracic legs long and slender, terminating in a curved claw. Copulatory appendage with billhook-shaped lappets, the right shorter than the left. Dirnensions. Holotype: 1979: carapace, LV. length 0.49 mm; height 0.26 mm. RV. length 0.48 mm; height 0.25 mm. Paratypes: 1979: 176 Q carapace, LV. length 0.52 mm; height 0.27 mm. RV. length 0.51 mm; height 0.27 mm. 1979: RV. length 0.47 mm; height 0.24 mm. 1979: LV. length 0.49 mm; height 0.24 mm. 1979: carapace, length 0.51 mm; height 0.30 mm; width 0.32 mm. 1979: carapace, length 0.53 mm; height 0.28 mm; width 0.31 mm. 1979: carapace, LV. length 0.49 mm; height 0.26 mm. RV. length 0.48 mm; height 0.26 mm. 1979: LV. length 0.49 mm; height 0.25 mm. 1979: 184 Q RV. length 0.49 mm; height 0.25 mm. Remarks. Xestoleberis claroculata sp. nov. is unlike other described species in the rather atypical carapace outline that lacks the usual rounded posterior end of the genus. It also atypically possesses a distinct ornamentation of pits likex. belhrnutu sp. nov., but these two species differ in the shape of the copulatory appendage lappets. Xestoleberis claroculata is a distinctive species that in life is white with a dark eye spot of clear calcite; this does not show in the illustrations owing to the coating used during electron microscopy. Xestoleberis erichtriebeli sp. nov. (Figs 41C-K, 42A-J, 44B, C) Derivation ofnume. After the late Dr Erich Triebel who described the first species ofxestoleberis from Galapagos. Diagnosis. Xestoleberis with oval/reniform carapace in lateral view ; almost parallel-sided in dorsal view, only slightly convex. Greatest length of carapace slightly below mid-height. Hinge paraperatodont. Sieve plates small but with five rows of sieve pores. Anterior marginal canals numerous, branching. Lappets ofcopulatory appendage nearly symmetrical, broad, boomerang-shaped. Teeth of mandible of two sizes, triangular and bristle-like. Terminal claws of 2nd antennae smooth and of equal length in both dimorphs. Holotype. 8 carapace, : 18 7, Mosquera Islet on marine algae. Material. 3 1 specimens from Mosquera Islet and Punta Suarez. Colour ofspecies. White. Distribution and ecology. Hood Island and Mosquera Islet on marine algae. Description. Carapace oval/reniform in outline incurved ventrally, especially in smaller male dimorph. Dorsal margin arched with greatest height slightly behind midpoint. Anterior narrowly rounded, posterior broadly rounded with an angular posteroventral outline in the female dimorph and a broadly convex posteroventral margin in the male. Shell surface smooth. Eye spot dark against the white shell in uncoated live material. Left valve larger than the right. Normal pores have small sieve plates with an off-centre setal pore and five rows of sieve pores. Hinge paraperatodont. Xestoleberis spot with a single crescent-shaped slit. Muscle scars with a broad, V-shaped, anterocentral frontal scar. Inner margin and line of concrescence do not coincide anteriorly and a broad vestibule is present. Anterior marginal canals branching, becoming single anterodorsally and anteroventrally 3

66 66 R. H. BATE ET AL Figure 39. Xestoleberk daroculatu sp. nov. A. Male RV., paratype 1979: 177 (~115). B. Female RV, paratype 1979: 184 (X 115). C. Male LV., paratype 1979: 178 (x 115). D. Female LV., paratype 1979: 183 ix 115). E-G, I. Internal view LV., external view LV., internal view RV., female carapace (X 1151 and ~nusclc scars (x 32.51, paratype 1979: 176. H, J. Ventral view (x 115) and enlargenient ofhairs and inargiiial setac on venter (x lk), male carapace, paratype 1979: 180.

67 OSTRACODS FROM GALAPAGOS AND ECUADOR 67 Figure 40. Xestoleberis claroculata sp. nov. A, C. Maxilla and 2nd antenna, male paratype 1979: 186 (~280). B, D. 1st Antenna and mandible, female paratype 1979: 176 (~300). E-G. Ist, 2nd and 3rd Thoracic appendages, male paratype 1979: 182 (X280). H. Sieve plate with seta, female paratype 1979: 184 (x 1.2K). I. Ventral marginal seta and pore canal aperture, male paratype 1979: 180 (x2.5k). J. Funnel normal pore aperture, female paratype 1979: 176 (x2.5k). K, L. Left and right copulatory organs,inaleholotype 1979: 181(~270).M.Dorsalview,femaleparatype 1979: 179(x115).

68 68 R. H. BATE ET AL (Fig. 44B). Some posteroventral canals also branch (Fig. 44C). First antenna sixjointed; 2nd antenna with two strong, smooth terminal claws in both dimorphs. Mandible bearing teeth of two sizes; three broad and triangular and six to seven bristle-like teeth. Copulatory appendage with almost symmetrical lappets, both broad and crescentic or boomerang-shaped (Fig. 42H, I). Dimensions. Holotype, 1979: carapace LV. length 0.42mm; height 0.22 inm. RV. length 0.41 mm; height 0.22 mm. Paratypes: 1979: RV. length 0.38 mm; height 0.20 mm. 1979: 189 Q carapace LV. length 0.48 nim; height 0.24 mm. RV. length 0.47 mm; height 0.26 mm. 1979: 190 Q RV. length 0.46 r i m ; height 0.25 mm. 1979: 409 Q RV. length 0.47 mm; height 0.25 mm. 1979: RV. length 0.47 mm; height 0.25 mm. 1979: carapace LV. length 0.47 mrn; height 0.24 mm. RV. length 0.45 mm; height 0.24 mm. 1979: RV. length 0.40mm; height 0.21 mm. 1979: LV. length 0.49 mm; height 0.25 mm. 1979: carapace, length 0.40 mm; height 0.22 nirn; width 0.20 mm. 1979: 415 Q carapace, length 0.49 mm; height 0.26 nim; width 0.23 mm. 1979: 416 Q RV. length 0.47 mm; height 0.25 mm. 1979: LV. length0.48 mm; height0.25 mm. Remarks. Xestoleberis erichtriebeli sp. nov., although of a shape that is similar to a number of species, has sufficient characters that are different to make a clear distinction possible. Xestoleberis arcturi Triebel, 1956, described from brackish water from the Galapagos Islands, is laterally similar although lacks the posteroventral upward sweep of the male, is not so strongly arched dorsally, and is more positively convex in dorsal view. The shape of the lappets of the copulatory appendage is quite dissimilar, those ofx. arcturi being rather long and narrow. The teririinal claws of the 2nd antenna in X. arcturi are dimorphic, one of the claws in the male bearing short bristles; these have not been observed in X. erichtrzebeli. Xestoleberis xaixaiensis Hartmann, 1974 from south Mozambique is closer to our species in the outline of the male dimorph but differs in having narrow, triangular lappets in the copulatory appendage. Xestoleberis tomkilenyii sp. nov. (Figs 42K-S, 43A-Q, 44F) Derivation ofname. After Dr T. I. Kilenyi for his work on noded ostracods. Diagnosis. Small, elongate Xestoleberis with up to three small nodes on posteroventrolateral part of carapace, not always equal number on each valve. Anterior marginal canals few. Copulatory organ large, rounded and symmetrical with small, triangular lappets. Male 2nd antenna with one of two claws bearing short bristles. Holotype. carapace, 1979: 418, Mosquera Islet on marine algae. Material. 232 specimens from Mosquera Islet and Hood Island. Colour $species. Reddish-brown; shell colourless. Distribution and ecology. Very common on Hood Island and less common on Mosquera Islet; live on marine algae. De.scription. Carapace small and slender, not excessively swollen in dorsal view although the female dimorph may be readily distinguished in this view by its more broadly Hattened posterior (Fig. 43C, J) ; the males taper slightly posteriorly (Fig. 43G). Slender in lateral view, the carapace is proportionally long for its height and the ends rather narrowly rounded, the anterior particularly so. Shell surface

69 OSTRACODS FROM GALAPAGOS AND ECUADOR 69 Figure 4 1, Xestoleberis claroculuta sp. nov. A, B. Hinge and Xestolebens spot, LV., female paratype 1979: 176(x 250).Xestoleberiserichhiebelisp.nov. C, E. RightandLV.,fernaleparatype 1979: 189(x 115). D, F. Right and lett valves, male holotype 1979: 187 ( X 115). G, J, K. Internal view (x 115) and enlargements of the hinge (x 350), fernale RV., paratype 1979: 190. H. Dorsal view, male carapace, paratype 1979: 414 (x 115). I. Dorsal view, female carapace, paratype 1979: 415 (x 115). 3*

70 70 R. H. BATE ET AL smooth with simple funnel pores (Fig. 43M) and larger sieve plates, each having a smooth rim and up to eight rows of sieve pores (Fig. 434). One to three small nodes may be developed on the extreme posterior portion of the ventrolateral surface. The number of nodes is normally unequal between the left and right valves. Left valve larger than the right, overreaching the right anteriorly and posteriorly, overlapping the right dorsally and ventrally. Hinge paraperatodont. Muscle scars with a V- or cloverleaf-shaped frontal scar and with the dorsal adductor scar three-rayed (Fig. 43H). Inner margin and line of concrescence do not coincide anteromedially and a small vestibule is produced; anterior marginal canals few and rather thick (Fig. 44F). First antenna six-jointed; 2nd antenna with median podomeres fused and terminal claws dimorphic: male having one claw bearing short bristles, the other claw smooth (Fig. 42M); both claws smooth in the female. Spinneret bristle of male bluntly rounded, pointed in the female. Copulatory appendage symmetrical, large, rounded, with small, pointed, triangular lappets. Dimensions. Holotype 1979: 418 carapace, length 0.35 mm; height 0.16 mm; width 0.17 mm. Paratypes: 1979: 419 Q carapace, length 0.36mm; height 0.19 mm; width 0.21 mm. 1979: 420 d LV. length 0.37 mm; height 0.18 mm. 1979: RV. length 0.35 mm; height 0.15 mm. 1979: carapace, LV. length 0.37 mm; height 0.17 mm. RV. length 0.36 mm; height 0.16 mm. 1979: 426 d carapace, LV. length0.35 mm; heighto. 17 mm. RV. length 0.34 mm; height 0.16 mm. 1979: carapace, length 0.36mm; height 0.17 mm; width 0.21 mm. 1979: carapace, length 0.34 mm; height 0.16 mm; width 0.20 mm. 1979: carapace, length 0.36 mm; height 0.18 mm; width 0.20mm. 1979:430 9 LV. length 0.36mm; height 0.18mm. 1979:431 8 carapace, length 0.35 mm; height 0.17 mrn; width 0.19 mm. 1979: carapace, length 0.37 mm; height 0.17 mm; width 0.20 mm. Remarks Xestoleberis tomhilenyii sp. nov. is of a similar size and appearance to X. chilensis Hartmann, 1962, X. rubrimaris Hartmann, 1964 and X. grucilis Brady, 1890 but dif fiers in the possession of small postero-ventrolateral nodes and in features of the copulatory appendage. ORIGIN OF THE GALAPAGOS OSTRACOD FAUNA The Galapagos islands are situated above a hot spot within a structural triangle known as the Galapagos Gore. According to Holden & Dietz (19721, movement of the lithospheric crust over this hot spot and the associated upwelling of oceanic magma, produced two diverging ridges, the Cocos and the Carnegie, that have the Galapagos islands at their apex. Calculating the seafloor spreading rate, Holden 8c IIietz are able to demonstrate the relationship of these two ridges during the Late Miocene ( 10 m.y.1 and the Mid Oligocene (30 m.y). According to their calculations the Galapagos Gore had its origin, above the Galapagos hot spot, at 40 m.y. Thus, from that time oceanic islands were being produced that would have provided sites for colonization and speciation. With crustal movement the Cocos and Carnegie ridges were established and a series of oceanic islands produced - some of which remain at the present time. Thus the present flora and fauna, although still having to find some mechanism for getting out to the oceanic islands (the distance from continental America could have been less than now exists between Galapagos and the Americas), would have had a longer period of isolation in which to speciate;

71 OSTRACODS FROM GALAPAGOS AND ECUADOR 71 Figure 42. Xestoleberiserichtriebeli sp. nov. A. Sieve plate, female paratype 1979: 416 (x3.25k). B. Muscle scars, female paratype 1979: 190 (~400). C-J. 2nd Antenna; 1st antenna; mandible;? 1st and? 2nd thoracic appendages and maxilla, female paratype 1979: 41 1 (~250). H, I. Copulatory appendages, male holotype 1979: 187 (x219).xestoleberistomril~~iisp. nov. K, L, Q-S. Mandible; 2nd antenna; lst, 2nd and 3rd thoracic appendages, female paratype 1979: 422 (x 250). M-P. 2nd Antenna; 1st antenna; maxillaand copulatoryorgan, male paratype 1979: 423 (~350).

72 72 R. H. BATE ET AL dispersal between existing and newly formed islands would not have posed an insuperable problem. With respect to our study, therefore, dispersal to the Galapagos could have commenced prior to the formation of the islands 1.4 m.y. ago. Unfortunately, the ostracod faunas from those islands that preceded the Galapagos and still remain (e.g. the Cocos Islands), have not been studied. A comparison is not therefore possible but it is considered probable that there would be some species in common. The ancestors of some of the Galapagos species have been traced (as will be seen later) back to the Pliocene of North Carolina, so for these species at least, dispersal westwards into the Pacific must have taken place in the Pliocene prior to the closure of the Isthmus of Panama. Whether any species currently recorded from the Galapagos Islands arrived in the area before the formation of the existing islands may only be surmised at when the faunas of the Cocos Islands are known. As far as the genus Galapagocythere is concerned, should rhis prove to be restricted to the Galapagos Islands then it is probable that it was derived from ancestral stock that existed in the area prior to the formation of the Galapagos. Distribution of North and South American faunas follows tracks that establish a pattern into which many species fit. Thus Rosen (1975: 444) illustrates six tracks of which the Eastern Pacific - Caribbean track is regarded as being the youngest. Where it is possible to demonstrate a dispersal route for the ostracods, the species generally relate to his E. Pacific-Caribbean track, slightly modified to incorporate the North Carolina and the Gulf coast regions. Our knowledge of the distribution of both fossil and Recent ostracods around the Caribbean, Gulf and north coasts of South America owes much to the work of van den Bold and it is through his work that we have been able to identify the fossil ancestors of some of the species described here. The fascinating plate tectonic theory for the origin of the Antilles, whereby crustal movements are considered to have thrust a part of the Pacific ocean floor through into the Atlantic (see Rosen, 1975: ), does not materially affect our study in that most of the species for which a fossil ancestor is known, appear to have arisen in the region of North Carolina. Indeed, the general distribution of the fossil species would appear to offer no support to this plate displacement theory. There is no necessity to explain the dispersal of the species by a geographical displacement of sites of development rather than by, as would appear more likely, an active dispersal of the ostracods themselves. A comparison of the ostracod faunas of the eastern Pacific and the Caribbean is riot possible for this paper as we have not sampled the waters beyond the littoral zone. Those species that are known to be living, or have ancestors outside the Galapagos Islands are discussed below. Caudites asymmetricus Pokorny, Studied previously from Galapagos by Pokorny ( 197 2), the genus Caudites appears to have successfully colonized the Galapagos Islands and to have speciated there - as evidenced by the very close relationship between C. sanctaecrucis E okorny, 1972 and our C. croca. According to McKenzie (1967a: 2311, Caudites developed in the Gulf-Caribbean region and dispersed outwards. Caudites asymmetricus certainly lends support to this postulate. First described by Pokorny

73 Figure 43. Xestoleberis sp. nov. A, B. Anterior and posterior parts of hinge, left valve male paratype 1979: 426 (~400). C. Dorsal view, female carapace, paratype 1979: 428 (X 115). D. Left side, male carapace, holotype 1979: 418 (x 115). E, F. Obliqueventralview to show nodes (two on LV., one on RV.) and left lateral view, female carapace, paratype 1979: 419 (x 115). G. Dorsal view, male carapace, paratype 1979: 431 (x 115). H, K. Muscle scars (~5501 and internal view, LV. (x 115), male paratype 1979: 420. I, 0, P. Internal view (x 115) and anterior and posterior hinge elements (x400), female RV., paratype 1979: 421. J. Ventralview, female carapace, paratype 1979: 432 (x 115). L. Right side, female carapace, paratype 1979: 427 (x 115). M, Q. Funnel pore and sieve plate, both with seta, female paratype 1979: 430 (x3.5k). N. Posterior ventral view of female carapace to show nodes, paratype 1979: 427 (~275).

74 '7 4 R. H. BATE ET AL from Galapagos, an almost identical form, also named C. asymmetricus, was figured by Hazel ( from the Pliocene of North Carolina and subsequently renamed c'. paraasymmetricus by Cronin 8c Hazel (1979). The two forms, although separate species, aze so close that an ancestor - descendant relationship is indicated. At the lsresent time, however (Fig. 451, no records exist between North Carolina and Galapagos. Radimella confragosa (Edwards, 1944) Like Caudites, Radimella was shown by Pokorny (1968, 1969) to be a common element of the Galapagos fauna, although when our material was collected live specimens were very rare. The species that interests us here (not recorded from Galapagos) is Radimella confragosa first described from the Duplin Marl (later dated as Pliocene by Hazel, 197 7) of North Carolina. It is still living at the present day off Ikuador but has not been recorded live from Central America. Radimella confragosa has been extensively recorded from around the Caribbean (Fig. 45) from Pliocene and Pleistocene sediments. It then disappeared (van den Bold, 19751, migrating into the Pacific before closure of the Isthmus of Panama. Touroconcha lapidiscola (Hartmann, 1959) and T. mosqueraensis sp. nov. These species belong to an ornate genus that has not yet been recognized outside the Central America-Mexico/Gulf-Caribbean region. The genus Touroconcha first appears in the Upper Miocene Spring Vale Formation of Trinidad (van den Bold, 1963); we consider the species concerned ancestral to the Recent T. lapidiscola. Touroconcha lapidiscola occurs at the present time off the Galapagos, Ecuador, Nicaragua and El Salvador and has been recorded by van den Bold (1966, 1977) from the Caribbean coast of Panama, Venezuela, Costa Rica and the Lesser Antilles. The development of this species from a Miocene ancestor in the Caribbean must have taken place in that area with later dispersal into the Pacific. l'ouroconcha mosqueraensis has only been found in the Mosquera Islet sample and is closely related to T. lapidiscola from which it is considered to have evolved. Loxoconcha (Loxocomiculum) occidentale sp. nov. and related species Within the Gulf-Caribbean region a number of closely related, pitted loxoconchids occur, especially in the shallow water lagoons of Texas. These probably developed from a common ancestor - Loxoconcha purisubrhomboidea Edwards, 1944 that appears in the Pliocene of North Carolina. Recent forms commonly referred to this species are in some instances known to be synonymous with L. matagordensis Swain, The matagordensis group of pitted loxoconchids is represented on the Pacific seaboard and Galapagos (Fig. 45) by L. (Loxocorniculum) Ienticuloides (Swain 8c Gilby, 1974) and in Galapagos alone by our L. (Loxocorniculum) occidentale. These two species, with L. (Loxocornicutum) matagordensis, represent a phylogenetic lineage that may be traced eastwards to the fossil L. purisubrhomboidea.

75 Figure 44. A. Xestolebm s belhta sp. nov., anterior vestibule and branching marginal canals (some simple) RV., paratype 1979: 166 (~289). B, C. Xestoleberis erichtriebeli sp. nov., anterior vestibule with branching marginal canals and ventrallpostero-ventral canals of same specimen. RV., paratype 1979: 409 (x 318). D. Xestolebm s defonna sp. nov., anterior vestibule with straight marginal canals, RV., paratype 1979: 168 (x277). E.Xestoleberislromotruncula sp. nov., anterior vestibule with marginal canals, note alternate long thin canals and thick, blind, canals. LV., paratype 1979: 175 (x 315). F. Xestoleberis tomkilenyii sp. nov., anterior duplicature with small central vestibule and short, thick, marginal canals. LV., paratype 1979: 422 (~400); G, H. Xestoleberis claroculota sp. nov., Xestoleberis spot with single crescentic slit. RV., paratype 1979: 176 (~900) and anterior vestibule with marginal canals. LV., paratype 1980: 121 (~329).

76 76 R. H. BATE ET AL. LIVING A LIVING FOSSIL 0 0 x + * I Figure 45. Distribution ofsome Galapagos and Ecuador species in relation to their fossil ancestors and living relatives. Paracytherideapinea sp. nov. Presently thought to be endemic to Galapagos, this species is morphologically so close to the more widely distributed P. tschoppi van den Bold, 1957 that it is possible to postulate that the latter is not only a living relative but is also the ancestor of our species. Paracytheridea tschoppi occurs both in the Pacific and the Caribbean at the present time and is recorded by Teeter (1975: 471) from the Miocene of the Caribbean and the Holocene of Florida, Trinidad and Panama. It thus fills all the requirements of being ancestral to P. pinea. Cytherelloidea a f.praecipua van den Bold, The species found in Galapagos has been referred to C. sp. aff. C. praecipua. Although there is insufficient material to be absolutely certain that the Galapagos species is separate from C. praecipua it would appear to be so. As the Galapagos form has not yet been recorded from elsewhere it is considered to have developed from C. praecifiua, recorded live from the Pacific coast of Mexico, from Clipperton Island and from the Caribbean (Trinidad and Tobago). The distribution of

77 OSTRACODS FROM GALAPAGOS AND ECUADOR 77 C. praecii,ua falls into the pattern of the other species described above having lineages traceable back into the Gulf-Caribbean area. In conclusion we would like to stress that although all the evidence points to an east-west dispersal route it may well be that a closer look at other species, those of the genus Xestoleberis for example, may well indicate dispersal in a north-south direction. We do not wish to imply that the Galapagos fauna originated, in its entirety, in the east. The Ecuador Tertiary and Quaternary ostracod faunas have been barely studied, although the presence of an active geosyncline in the region until the late Pliocene was not an environment conducive to the development of littoral species. Although Holden & Die& have indicated that land in the form of oceanic islands was present in the area now occupied by the Galapagos Islands, some 40 m.y. ago, the mechanism transporting the littoral ostracods to the islands needs to be considered. Considering the depth of water now and probable then, dispersal to the islands must have been passive, through the agency of oceanic currents. At the present time, the dominant current is the coldwater Humboldt that runs up the west coast of South America to turn west at the Equator and flow past the Galapagos, bringing cold water to these tropical islands (Fig. 1). The influence of this current appears to have been minimal as only Loxoconcha (L.) lenticuloides and Touroconcha lapidiscola are common to the islands and Ecuador, and even these could have arrived by an alternate route. This would be through the agency of the warm water Californian Current that periodically is able to reach the Galapagos during times of failure of the Humboldt. It is to this current (the El Niiio), or to a similar current, if dispersal commenced in the Tertiary, that we look for the agency of dispersal to the Islands. ACKNOWLEDGEMENTS Collection of marine algal samples from the Galapagos National Park was kindly permitted by the guides W. A. Cruz and K. D. Koch. It is also a pleasure to record sincere thanks to Dr C. R. Bristow (Institute of Geological Sciences, London) and his family for assistance and many kindnesses during the visit to Ecuadorin 1974 byoneofus(j.e.w.). Mr J. V. Brown (B.M.N.H.) photographed the ostracod appendages dissected by Carol Mayes while the marginal pore canal photographs used in Fig. 44 were taken by Mr P. V. York (B.M.N.H.). S.E.M. photographs were taken on a Cambridge Stereoscan Mk.2 and an IS1 scanning electron microscope by Dr J. E. Whittaker. Mrs Christine Whittaker drew Figs 1 and 45. REFERENCES ALLINSON, E. C. & HOLDEN, J. C., Recent ostracodes from Clipperton Island, EasternTropical Pacific. Transactions San Diego Natural History Society, 16: ATHERSUCH, J., The genus Xestoleberis (Crustacea: Ostracoda) with particular reference to Recent Mediterranean species. Pubblicazioni Stazione Zoologica Napoli, 40: ATHERSUCH, J. & WHITTAKER, J. E., On Loxoconcha elliptica Brady. Stereo-Atlas ofostracod Shells, 3: BATE, R. H., Upper Cretaceous Ostracoda from the Carnarvon Basin, Western Australia. Special Paper, Palaeontology, 10: BENSON, R. H., 1976a. On Radimelladictyon Pokorny. Stereo-Atlasof OstracodShells,3:41~4. BENSON, R. H., On Radimelladanuini Pokorny. Stereo-Atlas ofostracodshells,3: BENSON, R. H. & COLEMAN, G. L., Recent marine ostracodes from the eastern Gulf of Mexico. University ofkansas Paleontological Contributions, Arthropoda, 2: 1-52.

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