Recent marine Ostracoda from the Solomon Islands. Part 4: Cytheroidea; Hemicytheridae, Thaerocytheridae

Eleven species of family Hemicytheridae and seven of the family Thaerocytheridae are described. Together they comprise 14% of the total Recent ostracod fauna described from the Solomon Islands. In the main the hemicytherids are much more endemic than the thaerocytherids. Three new species have been recorded only from the Solomon Islands, and three species of Caudites, held in open nomenclature due to their rarity, are also probably endemic to the islands. Another three new species have been recorded only from Java and one species of Mimicocythere gen. et sp. nov. also occurs in Australia. The six new species described and illustrated are: Ambostracon (A.) micropapillatum, A. (A.) micromaculata, Caudites shortlandensis, ?C. atypicus, Mutilus dissimilis ssp. nov. and Mimicocythere pseudomelobesoides gen. et sp. nov. Only one of the hemicytherids, Caudites javana Kingma, occurs throughout the Indo-Pacific. It is the Thaerocytheridae, however, that are almost pandemic in tropical regions, with Tenedocythere deltoides and T. transoceanica being distributed particularly widely. A new species of the rare genus Neobuntonia, N. subalata sp. nov., only the second modern species to be described, is also illustrated.


INTRODUCTION
There has been a resurgence of studies of Ostracoda in the Indo-Pacific area. A listing of the most important publications is given in the introduction of recent papers by the present authors (Titterton & Whatley, 2005, 2006a and Warne et al. (2006).  Remarks. Ambostracon was originally erected by Hazel (1962) as a monotypic genus for a hemicytherid species found in sediments of Pleistocene age from California. Valicenti (1977) considered that Ambostracon and Patagonacythere Hartmann, 1962 (published some months later than Ambostracon) are subgenera of Ambostracon and distinguished them on the degree of the development of the anterior submarginal ocular ridge. This anterior ridge is weakly developed in A. (Patagonacythere) but in A. (Ambostracon) it forms an ocular ridge varying in strength between different species. Three species of Ambostracon were encountered in the present material and all possess an anterior submarginal ocular ridge and are referred to A. (Ambostracon).
Ambostracon is related very closely to several other hemicytherid genera. It is less caudate and more quadrate in outline than Caudites Coryell &Fields, 1937. Caudites andOrionina Puri, 1954 possess pillar structures within the anterior vestibulum, formed by the fusion of two lamellae. These structures are absent in Ambostracon. Ambostracon is more elongate and subrectangular in outline than the quadrate Mutilus Neviani, 1928, and the former lacks the vertically incised posterior tooth of the RV hinge characteristic of Mutilus and Aurila Pokorny, 1955. Subgenus Ambostracon (Ambostracon) Hazel, 1962 Ambostracon (Ambostracon) variornatum (Hartmann), 1978 (Fig. 4, nos 4, 5;Pl.  Material. Approximately 1000 valves and carapaces, A-3 to adult. Samples 1, 2, 13-15, 19, 29, 32, 55, 59, 61, 0S3-0S6 Guadalcanal and Shortland islands. Description. Surface of valve costate/reticulate with series of irregular ribs which may vary in development between individuals, with irregular intercostal reticulation and prominent pore conuli. Hinge holamphidont with smooth median element and lacking auriline toothlet in posterior terminal socket of LV. Central muscle scars comprise a single ventral and dorsal scar, two subdivided median scars and two subovate frontal scars.  Occurrence. Hartmann (1978) recorded A. (A.) variornatum from Recent eulittoral sediments from the western coast of Australia.
Remarks. This species does not belong to Mutilus Neviani, 1928 as the posterior tooth of the right valve hinge is not incised; rather, it is lobate, a common feature of many species of Ambostracon of both subgenera. Hartmann & Kuhl (1978) showed this species to be very variable in ornament, ranging from almost smooth to strongly reticulate and ribbed. Ambostracon (A.) micropapillatum sp. nov. of the present study differs in the position of the lateral ribs and it possesses distinctly pointed posterodorsal and posteroventral swellings. The females are more inflated than the male but both sexes are similar in size, the male being slightly less high.

Diagnosis.
A species of Ambostracon (Ambostracon), characterized by a strongly reticulate surface ornament, weakly concentric around the subcentral tubercle on which the reticulae are smaller with no lateral ribs and a secondary ornament of very fine papillae in the fossae. Distinct, sub-peripheral, ocular rib that extends into an antero-marginal rib, paralleling the margin and terminating at the anteroventral angle. Hinge holamphidont with smooth median element.

Diagnosis.
A species of Ambostracon (Ambostracon) with a distinct ocular rib and reticulate primary ornament, of which there is a strong, oblique orientation of the muri in the posterior region. Secondary ornament of fine papillae that are often elongated, except on crests of prominent muri. Valves swollen posterolaterally with conspicuous posteroventral and posterodorsal swellings. Hinge holamphidont with conspicuously crenulate median element. Description. Medium. Thick-shelled. Opaque. Sexual dimorphism conspicuous; male less high and less tumid than female. Subquadrate to subrectangular in lateral view: hastate in dorsal view. Anterior margin broadly rounded: extremity at midheight. Posterior margin narrower, bluntly caudate; more upswept in RV: extremity below mid-height. Dorsal margin gently arched, sloping to posterior: anterior cardinal angle rounded; posterior angle more prominent. Ventral margin with distinct oral concavity. Greatest length below mid-height; greatest height at anterior cardinal angle; greatest width at posterior third. RV slightly longer than LV but LV overlaps RV at cardinal angles. Valves with posterodorsal and a posteroventral swellings, subcentral tubercle not pronounced. Surface reticulate with distinct, subperipheral anterior ocular rib extends from the glassy eye tubercle and continues ventrally, subparallel to anterior margin with a slight interruption at the anteroventral angle, to the ventrolateral swelling. A less distinct rib extends anterolaterally for half the length from the posterodorsal swelling. Strong oblique orientation of reticular muri across the lateral surface in posterior region, more or less well developed in different individuals. Secondary ornamentation of very fine papillae, many of which are elongated, except on crests of prominent muri which are smooth. Npc few, evenly distributed, sieve-type, commonly on pore conulae. Inner lamella moderately wide, LOC and IM subparallel to OM: narrow crescentic anterior vestibule. Approximately 47-52 anterior and 39-41 posterior rpc; straight, simple, slightly inflated medianly. Sub-peripheral selvage, very strongly and broadly developed. Hinge holamphidont: RV anterior terminal element a bilobate tooth; anteromedian element a deep socket bounded ventrally by an anti-slip bar; anteromedian element a long, straight, denticulate groove with four small, widely spaced teeth distally; posterior terminal element a crescentic dentate ridge with 4-5 lobes; LV complementary. Central muscle scars small, ovate; median two adductor scars divided into two; dorsal and ventral scars single; two ovate frontal scars.

Dimensions.
Length Remarks. Coryell & Fields (1937) in their type description of the genus did not describe the distinctive pillar structures which are characteristic of Caudites, Orionina Puri, 1954, Anterocythere McKenzie & Swain, 1967and Palaciosa Hartmann, 1959 Caudites may be distinguished from the other five genera by its shape; being more elongate and caudate posteriorly and its costate ornament. Also, species of Orionina characteristically possess a reticulate surface ornament.

Diagnosis.
A species of Caudites, characterized by a prominent posterodorsal loop and an ornament of strong ribs with smooth intercostal areas. Subperipheral, ocular rib subparallels the anterior margin and then extends posteriorly as the ventrolateral rib. Anteriorly the rib is buttressed by distally notched or tooth-like, small ribs anteriorly. A prominent vertically aligned rib extends from posterodorsal swelling to the ventrolateral rib.

Dimensions.
Length Occurrence. As the synonymy shows, this is a very widespread species, in the Malaysian, Indonesian, Australian, Solomon Islands areas. Jain (1978: 122) reported it from the Gulf of Manaar, Ceylon (Sri Lanka), the Recent of the Persian Gulf and the Neogene of the Andaman Islands.
Remarks. The present species is very similar to Caudites sp. A and Caudites sp. B of the present study. All three species are similarly ornamented by a series of strong ribs with smooth intercostal areas and a prominent posterodorsal loop but may be distinguished by detailed study of the posterolateral ribs. In Caudites sp. A the posterolateral rib extends ventrally from the posterodorsal swelling and curves towards the posterior extremity; this rib in the present species is vertical. The ventrolateral rib also differs, in Caudites sp. A it is expanded medianly but in the present species it becomes expanded posteriorly. Caudites sp. B differs in that the rib extending ventrally from the posterodorsal loop bifurcates medianly; one rib branches towards the anterior and the other towards the posterior extremity. Caudites sp. B is also distinct in that the anterior ocular ridge is interrupted anteroventrally and there is no median dorsal tubercle. One of us (RCW) has seen original material of C. javana from the Kingma collection and this was illustrated by him with Zhao (Zhao & Whatley, 1989b). It is agreed that the two species attributed to C. javana by Keij (1953Keij ( , 1954 from the Java Sea and the Philippines respectively, are not conspecific with that species and represent two distinct species. Caudites cf.  Description. Small to medium. Thick-shelled. Opaque. Male smaller and less tumid than female. Subtriangular in lateral view, sub-elliptical in dorsal view. Anterior margin obliquely rounded with many, small, frill-like marginal denticles continuing into ventral margin; extremity at mid-height. Posterior margin strongly caudate; posterodorsal slope deeply concave: extremity subventral. Dorsal margin, straight, inclined posteriorly, overhung by lateral swelling so as to appear arched. Cardinal angles prominent, except anterior angle of RV. Ventral margin gently biconvex bearing frill-like marginal denticles except in oral region; posteroventrally four small but distinct, backswept marginal spines. Greatest length subventral; greatest height through anterior cardinal angle; greatest width through subcentral tubercle. LV overlaps RV at anterior cardinal angle. Valves inflated, posterodorsally below the posterior cardinal angle and posteroventrally. Conspicuous but small, glassy eye tubercle. Strongly ornamented by a series of numerous ribs and fine, irregular intercostal reticulation. An anterior subperipheral, ocular/anterior ridge bifurcates near the anteroventral angle, one short branch to anterior margin, second branch becoming the ventrolateral rib. A broad, oblique lateral rib extends from anteroventral marginal rib across subcentral tubercle and then posteriorly to meet a broad rib extending vertically from posterodorsal angle; at this point the latter rib becomes less broad and curves posteriorly to meet ventral margin near posterior extremity. A ventral rib curves from subcentral tubercle over posteroventral swelling, to join the strong posterior rib. A peripheral posterodorsal rib ends at posterior extremity. A strong rib curves over dorsal margin midway along its length and continues obliquely anteriorly to area below eye tubercle. Secondary ornamentation of very fine puncta in fossae and reticulae on broad ribs and subcentral tubercle. Npc few, large, widely distributed. Inner lamella wide: LOC and IM subparallel to OM, coincident except anteriorly where narrow crescentic vestibule occurs. Approximately 37 anterior and 29 posterior rpc, canals branching at posterior caudal process and particularly anteroventrally, others simple, all almost straight, slightly swollen medianly. Selvage robust, more peripheral in LV; wide, etched flange groove. Hinge holamphidont: RV anterior terminal element complex comprising a ventral single tooth on broader platform which becomes dentate dorsally with a ridge of six teeth; antero-median element a deep socket bounded ventrally by an anti-slip bar; posteromedian element a long groove becoming locellate posteriorly; posterior terminal element a long, irregular trilobate tooth; very narrow accommodation groove dorsally; LV complementary. Central muscle scars a vertical row of three, probably four, elongate adductor scars with two ovate frontal scars.

Dimensions.
Length Description. Elongate, subtriangular in lateral view: subelliptical in dorsal view. Anterior margin broadly rounded with many small, frill-like marginal denticles. Posterior margin strongly caudate. Ventral margin almost straight; slight, broad oral concavity. Dorsal margin straight, sloping towards posterior: cardinal angles prominent. Valves with a sharp, very prominent, posterodorsal swelling just below cardinal angle. A deep, short, oblique sulcus just posterior to glassy, inconspicuous eye tubercle. Surface of valves ornamented by a series of ribs, intercostal areas smooth. Approximately 29 anterior and 24 posterior rpc; many bifurcate anteriorly, almost straight, medianly inflated, evenly spaced. Selvage strong, narrow, subperipheral. Hinge holamphidont. Central muscle scars comprise a single dorsal ovate adductor scar; median two scars and ventral scar divided; three ovate frontal scars in vertical row.

Dimensions.
Length Remarks. The present species is most similar to and is probably closely related to C. javana Kingma and Caudites sp. B, both of the present study. These species may be distinguished by the pattern of the ribs, particularly postero-laterally (see remarks for C. javana).
Caudites sp. B (Fig. 4, nos 15 In both species the anterior ocular/anterior rib is interrupted anteroventrally but differs in the position of the posterior ribs. In C. albatrossi the rib extending ventrally from the postero-dorsal angle bifurcates; one branch anteriorly and the other continuing to the ventral margin; in the present species the posterior branch curves towards the posterior extremity. Caudites litusorienticola Hartmann (1981) from the subtropical east coast of Australia differs in possessing three approximately parallel ribs crossing the posterior half of the valve.
Caudites sp. C (Fig. 4, (Hu, 1979) specimens of the species from Jason Bay, SW Malay Peninsula. Caudites sanctaecrucis Pokorny, 1970, Recent, Galapagos Islands is also very weakly ornamented by ribs. The present species is ornamented even less strongly and possesses a short sulcus just posterior to the eye tubercle not present in C. sanctaecrucis and the dorsal rib does not curve along the entire dorsal margin as seen in the former. Caudites yambaensis Hartmann, 1981, Recent eulittoral, Eastern Australia, differs in that it possesses a short rib extending to the posterior extremity; this region of the caudal process is smooth in the present species. The two species are, however, very similar, as was also shown by the illustration of the former by McKenzie et al. (1990, pl. 6, fig. 2) from the Pleistocene of Goose Lagoon Drain, SE Australia. The prominent oblique lateral rib of Caudites propelevis Hartmann, 1981, also from the Recent eulittoral, Eastern Australia, distinguishes it from the present species. Caudites sublevis Bonaduce et al. (1980) from the Gulf of Aqaba is obviously of the same species group, but differs in its less arcuate dorsal margin and more numerous short horizontal ribs posterolaterally. The species described above is almost certainly new, but there are too few specimens to warrant the erection of a new species.

Derivation of name.
Greek conformable, with the prefix to denote the reverse atypikos. With reference to the fact that this species resembles Caudites in all respects except for the absence of pillar structures in the inner lamella.

Diagnosis.
A species questionably assigned to Caudites, with prominent swellings posterodorsally, posteroventrally and subcentrally. Surface ornament dominated by numerous lateral ribs radiating from subcentral tubercle, in particular two ribs to posterodorsal swelling with a third, short rib parallel to them, from the mid dorsal margin. Description. Small to medium. Thick-shelled, Opaque. Male less high and shorter than female. Subtriangular in lateral view: sub-elliptical in dorsal view. Anterior margin obliquely rounded, bearing numerous very small, frill-like marginal denticles which continue anteroventrally: extremity at mid-height. Posterior margin strongly caudate. Dorsal margin straight, inclined towards posterior, overhung by lateral tumidity to appear gently arched; cardinal angles acutely angled except anterior angle of RV which is rounded. Ventral margin gently biconvex; frill-like marginal denticles except orally. Greatest length subventral, through posterior extremity; greatest height through anterior cardinal angle; greatest width through subcentral tubercle. LV > RV, overlap at anterior cardinal angle. Valves swollen just below posterior cardinal angle, posteroventrally at two-thirds of the length and in area of subcentral tubercle. A strong ocular/ anterior marginal rib extends from anterior cardinal angle, with large glassy eye tubercle anterodorsally, parallels anterior and then becomes the ventro-lateral rib and terminating at the posteroventral swelling. A short rib bifurcates from the ocular rib to the anteroventral margin. A peripheral rib extends along the posterodorsal margin, sub-parallel to it a rib extends from the posterodorsal loop to the posteroventral angle. Lateral ornament dominated by ribs which radiate from the subcentral tubercle. A broad rib extends to anteroventral angle, crossing the ocular/anteromarginal rib; two parallel ribs extend to the posterodorsal loop with a third, shorter rib from the mid-dorsal margin that parallels these two ribs but does not reach the subcentral tubercle, and a short rib that extends vertically from the eye-tubercle towards the sub-central tubercle. Intercostal reticulation, variable in strength of development, but the muri are often strong and sharp posteriorly. Npc few, regularly distributed on ribs and muri of reticulation, usually as pore conuli, one conspicuous conulus midway along posterior peripheral rib. Inner lamella wide. Narrow crescentic anterior vestibule, elsewhere LOC and IM coincide, subparallel to OM. Approximately 42 anterior and 25 posterior rpc, slightly sinuous, most simple, some branching at caudal process. Strong selvage, becoming more peripheral posteriorly, particularly in LV: wide flange groove. Hinge holamphidont: RV anterior terminal element a strong tooth on wider platform; anteromedian element a deep socket bounded ventrally by an anti-slip bar; posteromedian element a long groove becoming locellate posteriorly to accommodate two denticles on LV hinge bar; posterior terminal element an elongate, irregular tooth. Central muscle scars not clear, small, ovate; four adductor scars in vertical row with at least one of the two central scars subdivided, two frontal scars.

Dimensions.
Length Occurrence. This species is also common in Quaternary brackish-water sediments from the Indespensable Reefs and offshore, Quaternary marine sediments from Guadalcanal (Whatley et al., in press b). Hartmann, 1981, Recent eulittoral of Eastern Australia, is remarkably similar but possesses cauditid pillar structures in its inner lamella, lacks the strong posteroventral swelling and also the strong median R. Titterton & R. C. Whatley ventro-lateral rib. The present species differs from ?Caudites mcmillani Whatley & Keeler, 1989 from the Recent of Réunion, which also lacks pillar structures in its inner lamella, in possessing three parallel, lateral ribs that extend obliquely from the posterodorsal margin, two to the subcentral tubercle. Another species they described, ?Caudites sp., also lacks pillars. It is, of course, possible that these three species could be considered as a new genus, based on the absence of the pillars. However, what was written then (Whatley & Keeler, 1989: 70), still holds good today:

Diagnosis.
A species of Mutilus, characterized by its robust ornament of numerous lateral ribs with intercostal reticulae. Ornament dominated by an oblique, lateral rib extending over subcentral tubercle and a series of four ribs radiating from prominent, posterodorsal loop. Ribs form a conspicuous rightangled triangle just posterior to subcentral tubercle. Posterior terminal element of right valve hinge a long, slightly irregular incised tooth.
Locality and horizon. Sample OS5, coral reefs to the east of Rokuai Island, off the northeast coast of Shortland Island. Coarse-grained coral sand. Recent.
Description. Medium. Thick-shelled. Opaque. Subquadrate to subovate in lateral view; irregularly spindle-shaped in dorsal view. Sexual dimorphism inconspicuous. Anterior margin broadly rounded: extremity below mid-height. Posterior margin bluntly caudate; a concave posterodorsal slope and a convex posteroventral slope. Dorsal margin very gently convex, slightly sloping, overhung posteriorly by lateral ornament; anterior cardinal angle rounded; posterior angle more pronounced. Ventral margin gently biconvex. Greatest length through posterior extremity, well below mid-height; greatest height through anterior cardinal angle; greatest width through posterolateral tumidity. LV>RV, overlaps along dorsal and anterodorsal margins. Strongly ornamented by numerous ribs and intercostal reticulae. Distinct, strong, subperipheral, ocular antero-marginal rib begins just dorsal to glassy eye-tubercle, parallels anterior margin and then becomes the ventro-lateral rib. A series of ribs radiate from postero-dorsal loop over the posterior cardinal angle. A prominent rib extends obliquely anteriorly to an area below eye tubercle, a second rib branches vertically from posterior end of first rib to mid-height where it almost undergoes a right angle to continue anteriorly, subparallel to the first rib. From this right angle of the second rib a short rib continues ventrally, then anteriorly joining the second rib again at the subcentral tubercle, forming a small right-angled triangle. A third, gently curved rib extends ventrally from the posterodorsal inflation, then posteriorly to meet the margin just below posterior extremity. A fourth, more posterior rib is subparallel to the third, meeting the margin at the posterior extremity. A strong ventrolateral rib develops into a small ala posteroventrally and continues as a weaker rib to posterior margin. Strong intercostal reticulae link the ribs, with secondary ornamentation of very fine etching on muri of primary reticula; less dense in fossea. Npc moderately numerous, large, sieve type, evenly distributed mainly on muri, some on pore conuli, particularly posteriorly. Inner lamella moderately wide: LOC and IM coincident, subparallel to OM. Rpc numerous: 63-65 anterior and 56-59 posterior canals; slightly sinuous, simple, closely spaced except in oral concavity, slightly inflated medianly. Selvage robust, subperipheral in RV; more distal in LV. Hinge holamphidont, very robust: RV anterior terminal element a strong ovate tooth vertically aligned; anteromedian element a deep smooth socket bounded ventrally by an anti-slip bar; posteromedian element a long, smooth groove; posterior terminal element a long, slightly irregular incised tooth; LV complementary. Central muscle scars small, ovate; median two adductor scars divided, dorsal and ventral sears single, two ovate frontal scars.

Length
Height  Hartmann, 1978, Recent eulittoral of Western Australia, in the pattern of the lateral ribs and detail of the lateral ornament, just posterior of the centre. Mutilus sp. illustrated by Jain (1978), from the Recent off Western India has less strongly developed lateral ribs. Mutilus (M.) oahueneis Holden, 1967, from the Neogene of Hawaii is about 0.2 mm longer, less inflated posterodorsally and differs in the detail of the reticulate ornament. Mutilus sp. described by Hartmann (1981) from the Recent eulittoral of NE Australia, differs in the detail of the surface ornament, particularly below the eye tubercle. Mutilus curvicostatus Howe & McKenzie, 1989 from Northern Australia, is obviously closely related, with its numerous ribs and the nature of its intercostal reticulation but differs significantly in the detail of the ornament. A remarkably similar species in shape, outline and ornament is Tenedocythere keralaensis Khosla & Nagori, 1989, Lower Miocene of South India, but it lacks auriline dentition. The presence of sexual dimorphism may be indicated by the large range in width of adults. A specimen confidently considered a male LV (OS 16354) can be compared with the female left valve (OS 16350); others range in morphology between these two extremes.

Derivation of name.
Latin, mimus (Greek µ .µ ) an imitator or mimic. With reference to the way in which this genus mimics such unrelated genera as Echinocythereis Henryhowella Puri, 1957a.

Remarks.
For a diagnosis and description, see the type species. This genus has caused considerable confusion. It seems to be monotypic and to be confined to Australasia and the Solomon Islands. The genus is very difficult to classify since it has many enigmatic characters. For example, it is close in its overall carapace morphology to Cythere melobesoides Brady, 1869. However, as originally pointed out by Dingle et al. (1990), Brady may have combined two species. He initially (1869) recorded C. melobesoides from Mauritius but, in 1880, he recorded it from off the Cape Peninsula of South Africa in some 275 m of water and from Australia. Dingle et al. (1990) stated that their material, from deep-water Quaternary deposits off SW Africa, is conspecific with that illustrated from Brady's Challenger collections by Puri & Hulings (1976, pl. 25, figs 1, 2) from which a lectotype was erected and it is agreed that this material is conspecific with the material illustrated by Brady (1880, pl. 12, figs 10, 11). The Australian material illustrated by Brady (1880, pl. 18, figs 1a-d) in some ways resembles the present species, especially in the rather truncated posterior margin, but (L=0.75 mm) is much larger and, although not conspecific with the African and Indian Ocean material, it is equally not the present species. The original Australian material in the Natural History Museum, London remains unstudied; however, it seems to be conspecific with that described by Howe & McKenzie (1989) from specimens in the Northern Territory Museum, in which an adult male is recorded as L=0.70 mm. These latter authors unfortunately, however, record neither the hingement nor the musculature of this collection, and its exact provenance is not given.
Mimicocythere differs from Cythere melobesoides s.l. in two important ways: first it has antimerodont rather than holamphidont hingement and, secondly, the second most dorsal of its adductor scars is clearly subdivided and it has two discrete oval frontal scars, while the latter species has four undivided adductors and a v-shaped frontal scar. It is also notably smaller, being approximately 0.50 mm long. Given its small size and its merodont hinge, the authors were initially tempted to consider even the largest individuals as juveniles, perhaps A-2 or A-3 juveniles of Henryhowella melobesoides (Brady). However, it is clear from the width and advanced nature of the inner lamella as illustrated herein, that the type species of Mimicocythere is certainly adult in character.

Derivation of name.
Latin; from the close, but entirely superficial resemblance, of this species to the largely South African trachyleberid species Henryhowella melobesoides (Brady, 1869).

Diagnosis.
A small to medium spinose species of Mimicocythere with antimerodont dentition. extremity at mid-height. Posterior margin blunter and subcaudate in RV, especially males; extremity below mid-height to sub-ventral in male RV and bearing strong marginal denticles. Dorsal margin straight to very gently convex and overhung in lateral view by dorso-lateral margin; sloping posteriorly. Ventral margin almost straight. Valves inflated posteroventrally. Eye tubercle small but conspicuous. Surface ornament strongly spinose. Rows of large and markedly smaller spines seem to be superimposed on the muri of a fundamental reticulation. The overall disposition of the rows of spines is approximately concentric about mid-point. Npc fairly numerous, simple but with some sieve-type pores in solae. Many large and some small spines are perforate. Inner lamella of medium width; avestibulate. Npc not seen. Hinge antimerodont: RV anterior terminal element a dentate ridge in which the seven teeth decline in size and height from the anterior; posterior similar but with nine or ten teeth, median element a rather coarsely locellate groove. Adductor scars a vertical row of four with the second scar being clearly subdivided. There are two oval frontal scars. There is a very deep ocular sinus under the anterior terminal hinge element. Occurrence. The species has also been recorded from the area of Port Darwin, Northern Australia (Warne et al., 2006) and eastern Australia by Yassini and co-workers (see synonymy).

Remarks. Externally the present species is somewhat similar to
Echinocythereis scabra (Münster) 1830, but can be distinguished from it by its more subovate outline and by the orientation of the spinose ornament. Neobuntonia subulosa (Brady), 1880 and N. subalata sp. nov. are also slightly similar but can be distinguished from the present species by their shape and lack of a strongly spinose ornament. In their record of Echinocythereis melobesoides (Brady), Howe & McKenzie (1989: 40, figs 134, 135) made mention of A-1 juveniles and it would be interesting to see if these were similar to the present material. Although only four specimens were found in the present material, enough occur in other collections to justify the erection of a new taxon. For example, there are three adult LV in the Natural History Museum, London from the type collection of the paper by Warne et al. (2006) and the material described by Yassini and his co-workers (see synonymy).
Subfamily Thaerocytheridae Hazel, 1967Genus Neobuntonia Hartmann, 1981 Type species. Neobuntonia sierbertorum Hartmann, 1981. Remarks. It is very difficult to classify this genus correctly as all too little is known about it because this is only the second modern species of the genus, which was originally established solely on three specimens. However, on the basis of its musculature, it is for the present placed temporarily in the Thaerocytheridae, notwithstanding Jellinek's (1993: 136)  Remarks. Quadracythere Hornibrook, 1952 and Tenedocythere are regarded here as closely related genera differentiated by the presence of strong ribs in the latter which are absent in the former. Bosasella Bonaduce, 1985 is considered a junior synonym of Tenedocythere, which is where Neohornibrookella and Paraquadracythere, both Jellinek, 1993, should also be subsumed. The exact nature of the relationship of Jugosocythereis Puri, 1957b to this group remains unknown but this latter genus does not seem to be a true thaerocytherid since two of its adductor scars are divided.
Tenedocythere deltoides (Brady, 1890) (Fig. 4, nos 17 Occurrence. This widespread Indo-Pacific species also occurs in Quaternary deposits from the Solomon Islands (Whatley et al., in press a) and among Recent sediments sent to the authors by Dr Maddocks from Madagascar, although she did not describe it there herself.

Remarks.
Tenedocythere apios (Whatley et al., in press a) from the Pitcairn group is probably closest in shape to T. deltoides but the former has much more robust ornament and a more pronounced caudal process.
Tenedocythere transoceanica (Teeter, 1975) (Fig. 4,  Occurrence. As its synonymy shows, this is a very common and widespread species in the Indo-Pacific. In the Solomon Islands it was encountered by Hughes (1977 MS) in Miocene deposits from Nendö on Guadalcanal and in the Quaternary of the Indispensable Reefs and offshore Guadalcanal (Whatley et al., in press a).
Remarks. The present material is rather less punctate on the crests of the major ribs than in most populations. Occurrence. Over 600 valves and carapaces were found in Quaternary shallow-water marine sediments from offshore Guadalcanal by Williams (1980 MS). This will be described as a new species by Whatley et al. (in press a).

Diagnosis.
A large subquadrate to subrectangular species of Tenedocythere with strong ribs and strong intercostal reticulation, the muri of which are strongly punctate, each puncta bearing a small, central papilla.

Dimensions.
Length Height A-1 LV, OS 16388 0.60 0.36 A-2 RV, OS 16389 0.45 0.26 Occurrence. This species is fairly common in Quaternary sediments from the Indispensable Reefs and offshore Guadalcanal (Williams, 1980 MS). It will be described as a new species shortly (Whatley et al.,in press a).