sm. loas Zoology Series HISTORY MUSEUM VOLUME 62 NUMBER2 28 NOVEMBER 1996 The Bulletin of The Natural History Museum (formerly: Bulletin of the British Museum (Natural History) ), instituted in 1949, is issued in four scientific series, Botany, Entomology, Geology (incorporating Mineralogy) and Zoology. The Zoology Series is edited in the Museum’s Department of Zoology Keeper of Zoology Dr C.R. Curds Editor of Bulletin: Dr N.R. Merrett Assistant Editor: Dr B.T. Clarke Papers in the Bulletin are primarily the results of research carried out on the unique and ever- growing collections of the Museum, both by the scientific staff and by specialists from elsewhere who make use of the Museum’s resources. Many of the papers are works of reference that will remain indispensable for years to come. All papers submitted for publication are subjected to external peer review for acceptance. A volume contains about 160 pages, made up by two numbers, published in the Spring and Autumn. Subscriptions may be placed for one or more of the series on an annual basis. Individual numbers and back numbers can be purchased and a Bulletin catalogue, by series, is available. Orders and enquiries should be sent to: Intercept Ltd. P.O. Box 716 Andover Hampshire SP10 1YG Telephone: (01264) 334748 Fax: (01264) 334058 Claims for non-receipt of issues of the Builetin will be met free of charge if received by the Publisher within 6 months for the UK, and 9 months for the rest of the world. World List abbreviation: Bull. nat. Hist. Mus. Lond. (Zool.) © The Natural History Museum, 1996 Zoology Series ISSN 0968-0470 Vol. 62, No. 2, pp. 71-132 The Natural History Museum Cromwell Road London SW7 5BD Issued 28 November 1996 Typeset by Ann Buchan (Typesetters), Middlesex Printed in Great Britain by Henry Ling Ltd., at the Dorset Press, Dorchester, Dorset Bull. nat. Hist. Mus. Lond. (Zool.) 62(2): 71-82 Issued 28 November 1996 Indian Ocean echinoderms collected during the Sindbad Voyage (1980-81): 3. Ophiuroidea and Echinoidea ANDREW R.G. PRICE Ecosystems Analysis and Management Group, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK THE NATURAL 1} HISTORY MUSEUM FRANCIS W.E. ROWE 100ca Goldbrook Boarding Kennels, Nuttery Vale, Cross Street, Hoxne, Suffolk {P21 5BB, UK 11 ev 1990 PRESENTED GENERAL LIBRARY Synopsis. At least 44 ophiuroid and 11 echinoid species are recorded from echinoderm collections made during an international expedition, the Sindbad Voyage, from Oman to China. Sampling localities include the little known Lakshadweep (Laccadive), Islands and Pula Wé (Sumatra) from which 71% of the species were recorded. Following the zoogeographic subdivisions of Clark & Rowe (1971), range extensions are recorded for ten of the ophiuroids: W. India (Amphioplus (Lymanella) sp.); Sri Lanka (Ophiactis modesta, Ophiarachna robillardi, Ophiodyscrita instratus); Maldives area (Cryptopelta granulifera, Ophiochaeta hirsuta); and Indonesia / East Indies (Amphiura (Amphiura) dejectoides, Amphiura (Amphiura) micra, Amphioplus (Amphioplus) stenaspis, Ophiogymna pellicula). In addition to the taxonomic treatment, ecological information for each echinoderm species (habitat types, depth range) is provided and broadly analysed. INTRODUCTION The systematics and distribution of Indian Ocean ophiuroids and echinoids are treated in detail by Clark & Rowe (1971). Regions for which limited information is available include the Lakshadweep (Laccadive) Islands, Sumatra and other parts of SE Asia. Recent studies including the systematics and zoogeography of ophiuroids and echinoids for the Lakshadweeps include Nagabhushanam & Rao (1972) and James (1989), the latter yielding many new species records for both echinoderm classes, which fill in gaps in the distribution records of Clark & Rowe (1971). Recent work has also been undertaken in SE Asia, including Indonesia (Aziz, 1981) and the west coast of Thailand (Bussarawit & Rowe, 1985; Bussarawit, in prep.). This paper reports on collections of ophiuroids and echinoids from these areas and other localities during an international, transdisciplinary voyage across the Indian Ocean from Oman to China. The expedition, Sindbad Voyage, was undertaken in 1980-81 aboard a replica of an ancient Arab sailing vessel, “Sohar’. In addition to a systematic account, the zoogeographic significance of the results and the ecology of each species are broadly assessed. Details of the holothurian collections (Price & Reid, 1985) and asteroid collections (Marsh & Price, 1991) resulting from the expe- dition have already been published. Details of the crinoids collected are also being prepared (Marshall & Price, in prep.), and a detailed analysis of the ecology and biogeography of all five echinoderm classes will follow. Address for correspondence: First author © The Natural History Museum, 1996 MATERIALS AND METHODS Specimens were collected by one of us (A.R.G.P.) and other expedi- tion members from localities at Muscat, Oman; Chetlat, Laks- hadweeps (Laccadives); SW India; SW Sri Lanka; and Pula Wé, Sumatra. Details of the sampling localities are shown in Figure 1. Sampling was undertaken principally on coral reefs using scuba. At each locality details of habitat type and depth range were recorded, along with the number of individuals of each species. The number of specimens collected is placed in parenthesis after each station number in the Material lists for each species. Material was fixed and preserved using standard methods (Lin- coln & Shields, 1979). Although several specimens (inadvertently included with the asteroid collections) had been identified earlier by L.M. Marsh and a few preliminary identifications were made in the field by A.R.G.P., specimens were mostly identified by and all species confirmed by F.W.E.R. who is also responsible for taxo- nomic comments. The ophiuroid and echinoid collections are deposited at the Natural History Museum, London, where the holothurian collection (Price & Reid, 1985) and a representative collection of the asteroids (Marsh & Price, 1991) have also been lodged. Following recent practice (e.g. Sloan, Clark & Taylor, 1979), systematic references are kept to a minimum by citing major works when possible (e.g. Clark & Rowe, 1971; Clark & Courtman Stock, 1976; Cherbonnier & Guille, 1978; Rowe & Gates, 1995) from which the original species descriptions, recent authoritative diag- noses and taxonomic decisions can be traced. In some instances, further references are given (e.g. Sloan et al., 1979) to provide additional systematic or biological information. 72 A.R.G. PRICE AND F.W.E. ROWE ) 90 100 Muscat OMAN Chetlats ANDAMANS$ 3 LACCADIVES «,° ‘s 5 SRI LANKA NICOBARS +! e Tangalla Om ve ono 0 MALDIVES — ~ a °o ma Ug Bau Fig. 1. (a) Map of northern Indian Ocean showing sampling areas (¢) during Sindbad Voyage, with insert (b) for Pula Wé Sumatra. INDIAN OCEAN ECHINODERMS RESULTS Class Ophiuroidea Family GORGONOCEPHALIDAE 1. Astroboa nuda (Lyman, 1874) SEE. Clark & Rowe, 1971: 78; 92; Clark & Courtman Stock, 1976: 108; 130; Baker, 1980: 60; Rowe & Gates, 1995: 364. 810504D/3 (1), 810504D/4 (1). NW Klah, Pula Wé, Sumatra. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. Subtidal rock/coral; 13 m. Family AMPHIURIDAE 2. Amphiura (Amphiura) dejectoides H.L. Clark, 1939 SEE. Clark & Rowe, 1971: 80; 97; Cherbonnier & Guille, 1978: 38: MATERIAL. 810S01E/8 (4); ?810428D/5 (2). COLLECTION SITES. Ug Tapa Gadja & Ug Seukundo, Pula Wé, Sumatra. HABITAT AND DEPTH. Subtidal rock / coral, coral reef; 10 & 15 m. REMARKS. The specimens from stn 810501E/8 appear to accord well with the original description (Clark, 1939) of the species and descriptions in Clark & Rowe (1971) and Cherbonnier & Guille (1978). The 2 specimens from stn 810428D/5 differ in their firmer disc, with coarser ventral scaling and in having 6 arm spines proximally instead of fine ventral scaling and 5 proximal arm spines. They are identified as A. dejectoides with reservation. Clark (in Clark & Rowe, 1971) suspected Amphiura inhacensis Balinsky may be conspecific with A. dejectoides H.L. Clark, a conclusion con- firmed by Cherbonnier & Guille (1978). The records included herein extend the distribution of this species eastwards across the Indian Ocean from the Red Sea, East Africa and Madagascar to the Indo- Malayan region. In the latter region it may prove to be widespread. 3. Amphiura (Amphiura) micra H.L. Clark, 1938 SEE. Clark & Rowe, 1971: 80; 97; Cherbonnier & Guille, 1978: 46; Rowe & Gates, 1995: 350. MATERIAL. 810423B/2 (1). COLLECTION SITES. Ug Bau, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral, coral reef; 10—30 m. REMARKS. This species is recorded across the tropical coast of Australia and from Madagascar. Its discovery at Pula Wé suggests a wider distribution in the Indo-Malayan region for this very small species. V3 4. Amphiura (Amphichilus) ochroleuca (Brock, 1888) SEE. Clark & Rowe, 1971: 78; 100; Rowe & Gates, 1995: 344. 810502C/1 (1), 810427B/3 (1). SE Klah, SE Lho Pria Laot, Pula Wé, Sum- MATERIAL. COLLECTION SITES. atra. HABITAT AND DEPTH. In sponge and on subtidal rock; 0-10 m. REMARKS. This species is known from the Indo-Malayan region and more or less circumscribes the Australian continental coastline (Rowe & Gates, 1995). Pula Wé appears to be the most westerly point of its distribution known to date. 5. Amphioplus (Amphioplus) stenapsis H.L. Clark, 1938 SEE. Clark & Rowe, 1971: 78; 101; Rowe & Gates, 1995: 344. 810422B/4 (1). Nr. Klah / Seukundo, Pula Wé, Sumatra (disc MATERIAL. COLLECTION SITES. only). HABITAT AND DEPTH. Coral reef, 2—8 m. REMARKS. Although the single specimen comprises only a com- plete disc with the bases of 2 arms (6 & 9 segments respectively), there is little doubt of its identity. This record extends the range of the species to Pula Wé from its type locality, Darwin, N Australia. The record of A. stenapsis from Madagascar by Cherbonnier & Guille (1978) is almost certainly based on a misidentification, judging by the very small size of the radial shields of their specimens. The confirmation of this species in the western Indian Ocean therefore requires confirmation. 6. Amphioplus (Lymanella) sp. MATERIAL. 810109A/Ib (2). COLLECTION SITES. Beypore, India (west coast). HABITAT AND DEPTH. Subtidal mud, 9 m. REMARKS. Only the mouthparts and bases of the arms are avail- able to identify this taxon, which clearly represents a species of Amphioplus (Lymanella). The dorsal arm plates are trilobed, sug- gesting either species A. (L.) andreae (Liitken, 1872) or A. (L.) laevis (Lyman, 1874) in the key provided by Clark & Rowe (1971: 102). Cherbonnier & Guille (1978) indicate that /aevis has a wide range in the Indian Ocean and Indo-Malay region, whereas Clark & Rowe (1971) record andreae only from the Malay region. Without complete specimens it is not possible to determine the species nor indeed whether andreae and laevis are taxonomically separable. Family OPHIACTIDAE 7. Ophiactis modesta Brock, 1888 SEE. Clark & Rowe, 1971: 105; Rowe & Gates, 1995: 379. MATERIAL. 810206A/8 (3). COLLECTION SITES. Negombo, Sri Lanka. HABITAT AND DEPTH. Coral/rock; 5 m. 74 REMARKS. The 3 specimens were collected in a batch of 6 from stn 810206A/8 with 3 specimens of O. savignyi. They run unequivocably to the species O. modesta in the key provided by Clark & Rowe (1971: 105) where the relationship with other conge- ners is discussed by A.M. Clark (notes 25—27, pp. 103—105). Rowe (in Rowe & Gates, 1995) preferred to follow the views of Clark & Rowe (1971) regarding recognising the validity of the species O. modesta, a course also followed herein, rather than accept the sweeping synonymy of O. savignyi, which includes O. modesta, given by Cherbonnier & Guille (1978). 8. Ophiactis savignyi (Miiller & Troschel, 1842) SEE. Clark & Rowe, 1971: 82; 103; Clark & Courtman Stock, 1976: 164; Cherbonnier & Guille, 1978: 125; Sloan et al., 1979: 102; Price, 1983: 61; Rowe & Gates, 1995: 380. MATERIAL. 810206A/3 (5), 810206A/8 (3), 810426A/2 (1), 810501E/1 (1), 810501G/3 (1), 8105011/2 (1), 810502F/4 (2). COLLECTION SITES. Negombo, Sri Lanka; W Rubiah, Ug Seukundo, E Klah, Pula Wé, Sumatra. HABITAT AND DEPTH. 5-14 m. Sponge, coral/rock, subtidal rock, coral reef; REMARKS. The specimens identified here are fissiparous and 6- armed with trilobed dorsal arm plates and proximally 6 arm spines, according well with the key characters given in Clark & Rowe (1971). Family OPHIOTRICHIDAE 9. Gymnolophus obscura (Ljungman, 1867) SEE. Clark & Rowe, 1971: 82; 117; Rowe & Gates, 1995: 411. 810124A/11 (1), 810125A/2 (1), 810430A/20d (2). COLLECTION SITES. Ala Gala & Deumba Gala, Galle, Sri Lanka; Ug Seukundo, Pula Wé, Sumatra. MATERIAL. HABITAT AND DEPTH. Coral reef and epizoic on crinoids on subtidal rock; 8-15 m. REMARKS. This species is commonly epizoic on comasterid crinoids, the host species for which have not been identified for the specimens recorded herein. 10. Ophiothela danae Verrill, 1869 SEE. Clark & Rowe, 1971: 84: 116; Clark & Courtman Stock, 1976: 141; Price, 1983: 63; Rowe & Gates, 1995: 419. MATERIAL. 810125B/1 (3), 810206A/3/28 (4), 810425F/8 (10+), 810428A/2 (7), 810428A/14 (3), 810501A/3 (30+), 810501 A/4 (1), 810428B/1 (2), 810428D/3c (3), 810501E/9 (15+). COLLECTION SITES. Ala Galla, Galle & Negombo, Sri Lanka; N. Udjung Lo Me (NE Sabang Bay), Ug Bau, Ug Seukundo, Ug Tapa Gadja, Pula Wé, Sumatra HABITAT AND DEPTH. Epizoic on macroalgae, gorgonian, fire coral (Millepora sp.) sponge and on holothurians (Thelenota ananas), all on rock /coral; 2—30 m. A.R.G. PRICE AND F.W.E. ROWE 11. Ophiothrix exigua Lyman, 1874 SEE. Clark & Rowe, 1971: 84; 110; Cherbonnier & Guille, 1978: 140; Rowe & Gates, 1995: 422. 810206A/8 (5), 810502C/1 (2), 810502E/2 (3). Negombo, Sri Lanka; E Klah, Pula Wé, MATERIAL. COLLECTION SITES. Sumatra. HABITAT AND DEPTH. rock; 5—10 m. Coral/rock, sponge on coral reef and subtidal REMARKS. One specimen from stn 810206A/8, both from 810502C/1 and two from 810502E/3 are very juvenile specimens. 12. Ophiothrix savignyi (Miiller & Troschel, 1842) SEE. Clark & Rowe, 1971: 84; 109; Cherbonnier & Guille, 1978: 142; Price, 1983: 65. MATERIAL. 801114B/1 (1). COLLECTION SITES. Muscat, Oman (1 specimen). HABITAT AND DEPTH. Coral reef; 2 m. 13. Ophiothrix trilineata Liitken, 1869 SEE. Clark & Rowe, 1971: 84; 111; Clark & Courtman Stock, 1976: 145; Sloan et al, 1978: 103; Rowe & Gates, 1995: 423. MATERIAL. 810420A/5 (2), 810422B/3 (3), 810426A/2 (1), 810428A/9 (2), 810428C/7 (1), 810428D/3a&b (6&2), 810430A/8 (1), 810430A/18 (1), 810430A/21c (1), 810501D/2 (1), 810501E/2 (3), 810501E/5 (1), 810501E/8 (1), 810501E/9 (2), 810501E/11 (1), 810502F/2 (1), 810501F/3 (1), 810501G/1 (2), 810501G/3 (1 & 1 juvenile), 810501G/5 (3), 810502C/2 (1 very juvenile), 810502D/4 (4), 810502E/3 (4 juvenile), 810502F/2 (2 juvenile), 810502G/3 (2 juvenile). COLLECTION SITES. Klah/E Klah, Nr. Seukundo, Ug Seukundo, Pula Wé, Sumatra, W Rubiah, Ug Bau, Ug Tapa Gadja, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral reef, soft coral / gorgonian, subtidal rock, sponge/subtidal rock, sponge; 2-30 m. REMARKS. The majority of specimens exhibit the characteristic arm colour pattern of 5 longitudinal lines alternating white and dark blue. However, a few specimens bear a wide median pale longitudi- nal line along the arms, and at least one specimen (810501E/2) is distinctively patterned with cream blotches, the linear pattern being discernable only near the ends of the arms (see Clark & Rowe, 1971: 111). Next to O. (A.) purpurea, this is the most common ophiuroid species collected. 14. Ophiothrix (Acanthophiothrix) armata Koehler, 1905 SEE. Clark & Rowe, 1971: 84; 111; Rowe & Gates, 1995: 423. 810422B/4 (15+), 810502F/6 (2). Klah / Nr. Seukundo, Pula Wé, Sumatra. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. Coral reef, 2—8 m. REMARKS. This species is recorded from the Indo-Malay region, tropical Australian coasts and the South Pacific (Clark & Rowe, INDIAN OCEAN ECHINODERMS 1971). The present record is the most westerly so far known for the species. 15. Ophiothrix (Acanthophiothrix) purpurea von Martens, 1867 SEE. Clark & Rowe, 1971: 86; 112; Cherbonnier & Guille, 1978: 148; Sloan et al., 1978: 103: Rowe & Gates, 1995: 423. MATERIAL. 810204A/4 (3), 810421A/2 (1), 810421A/9 (1 juve- nile), 810421B/1 (1), 810422D/3 (2), 810423A/4 (1), 810423B/2 (1), 810425D/2 (1), 80425D/4b (1), 810425F/7 (7), 810425F/8 (1), 810426A/2 (3), 810427A/2 (2), 810428A/2 (2), 810428A/7 (3), 810428A/8 (4), 810428A/9 (2), 810428D/3f (23), 810430A/3 (1), 810430A/21c (6), 810430A/22b (1), 810430A/26 (5), 810501 A/1 (1), 810501A/2 (1 juvenile), 810501A/4 (1 juvenile), 810501A/6 (9), 810SO01E/7 (2), 810501E/9 (1), 810501E/14 (1), 810501E/15 (1), 810504B/2 (1). COLLECTION SITES. SW Kalpitiya, Sri Lanka; Ug Bau, Rubiah, Ug Seukundo, Ug Tapa Gadja, N Klah, ?N. Udjung Lo Me, NE Sabang Bay, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral reef, soft coral, fire coral (Millepora sp.), subtidal rock/coral (epizoic on soft coral / gorgonian & crinoid, sponge); 2-30 m. REMARKS. The most common ophiuroid species collected. 16. Ophiothrix (Acanthophiothrix) spinosissima Koehler, 1905 SEE. Clark & Rowe, 1971: 86; 112. 810422B/4 (4), 810501G/5 (2), 810502F/6 (1). Ug Seukundo, Klah/ Ug Seukundo, Pula Wé, MATERIAL. COLLECTION SITES. Sumatra. HABITAT AND DEPTH. Coral reef, 2—8 m. REMARKS. The specimens run down well to O. (A.) spinossima in the key provided by Clark & Rowe (1971). However, 2 specimens from stn 810422B/4 have a single dark line running the length of the dorsal side of the arms, rather than a series of dark spots. 17. Macrophiothrix aspidota (Miller & Troschel, 1842) SEE. Clark, 1968: 285; Clark & Rowe, 1971: 114; Clark & Courtman Stock, 1976: 137; Hoggett, 1992: 91. MATERIAL. 810123B/6 (1), 810124A/8 (1), 810206A/6 (1), 810206A/7 (1). COLLECTION SITES. Galle, Sri Lanka. Negombo, Closenburg Point, Galle, Ala Gala, HABITAT AND DEPTH. Subtidal rock, coral / rock; 5-15 m. 18. Macrophiothrix demessa (Lyman, 1861) SEE. Clark, 1968: 289; Clark & Rowe, 1971: 82; 114; Hoggett, 1991: 1089; 1992: 117; Rowe & Gates, 1995: 412. 801212B/1 (1), 810424B/4 (2). COLLECTION SITES. Chetlat, Lakshadweep (Laccadive) Islands; Seulakoe, Pula Wé, Sumatra. MATERIAL. 75 HABITAT AND DEPTH. Coral rubble, coral reef; 8 m & 20-30 m. REMARKS. A.M. Clark (1968) transferred this species to the genus Macrophiothrix referring Ophiothrix (Amphiophiothrix) H.L. Clark, 1946, of which demessa is type (and only) species to the synonymy of Macrophiothrix H.L. Clark, 1938. 19. Macrophiothrix elongata (H.L. Clark, 1938) SEE. Clark, 1968: 291; Clark & Rowe, 1971: 82; 114; Price, 1983: 61; Hoggett, 1992: 125. MATERIAL. 801111A/5 (1), 801114A/5 (2), 801114B/2 (1). COLLECTION SITES. Muscat harbour, Oman. HABITAT AND DEPTH. m. Coral reef, subtidal rock/coral/sand; 0.5—3 20. Macrophiothrix longipeda (Lamarck, 1816) SEE. Clark, 1968: 300; Clark & Rowe, 1971: 82; 114; Clark & Courtman Stock, 1976: 139; Hoggett, 1991: 1103; Hogett, 1992: 151; Rowe & Gates, 1995: 413. MATERIAL. 801212B/3 (1), 810206A/5 (1), 810430A/24a (1). COLLECTION SITES. Chetlat, Lakshadweep (Laccadive) Islands; Negombo, Sri Lanka; Ug Seukundo, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral/rock, coral rubble; 5—10 m. 21. Macrophiothrix lorioli A.M. Clark, 1968 SEE. Clark, 1968: 302; Clark & Rowe, 1971: 82; 115; Hoggett, 1991: 1108; Hoggett, 1992: 161; Rowe & Gates, 1995: 414. 810502D/2 (1), 810502E/1 (1). E Klah, Pula Wé, Sumatra. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. Coral reef, coral reef/subtidal rock; 5 & 10 m. 22. Macrophiothrix nereidina (Lamarck, 1816) SEE. Clark & Rowe, 1971: 86; 107 (as Ophiothrix (Keystonea) nereidina); Hoggett, 1992: 228 (as Macrophiothrix); Rowe & Gates, 1995: 426 (as O. (Keystonea) nereidina). MATERIAL. 810421A/4 (1), 810422B/3 (2), 810430A/20d (1), 810430A/21c (2), 810430A/22b (1), 810501E/6 (1). COLLECTION SITES. Ug Seukundo, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral reef, coral / rock; 2-10 m. REMARKS. The species nereidina (which was placed in the subgenus Ophiothrix (Keystonea) by A.M. Clark, 1967) is included herein in the genus Macrophiothrix. Hoggett (1991) stated that ‘it is particularly difficult to determine the respective boundaries between Macrophiothrix H.L. Clark, 1938 and two subgenera of Ophiothrix, O. (Placophiothrix) H.L. Clark, 1938 and O. (Keystonea) A.M. Clark, 1967. The differences between these taxa have traditionally relied principally on arm length, shape of dorsal arm plates, relative spinular armament of the disc plates including cover of the radial plates (see A.M. Clark, 1967; Clark & Rowe, 1971). The difficulty in recognising the supraspecific limits of these taxa is made all the more obvious by the treatment of the species Macrophiothrix 76 propinqua, placed in the subgenus Keystonea by A.M.Clark (1967), whilst Devaney (1974) described O. (Placophiothrix) westwardi which has been considered conspecific with propinqua by Hoggett (1991). Later, in a far-reaching and critical treatment of Macro- phiothrix, Hoggett (1992: PhD thesis) commits both the taxa Placophthiothrix and Keystonea to the synonymy of Macrophio- thrix, transferring the included species of the former two taxa to the latter taxon and to whom this move is herein credited. 23. Macrophiothrix propinqua (Lyman, 1861) SEE. Clark & Rowe, 1971: 86; 107 (as Ophiothrix (Keystonea) propinqua); Clark, 1980: 537; Hoggett, 1991: 1130; Hoggett, 1992: 204; Rowe & Gates, 1995: 415. MATERIAL. 810428D/5 (5), 810501C/3 (1 juvenile), 810501D/1 (1 juvenile), 810501E/13 (1), 810501DF/1 (1 juvenile), 810501G/1 (1), 810501G/5 (3), 810S011/2 (2), 810502F/3 (1), 810502G/3 (1). COLLECTION SITES. Ug Tapa Gadja, Ug Seukundo, E Klah, Pula Wé, Sumatra. HABITAT AND DEPTH. soft coral; 2-20 m. Subtidal rock/coral, coral rubble, coral reef, REMARKS. This species was first transferred to the genus Macrophiothrix H.L. Clark, 1938 by A.M. Clark (1980) from Ophiothrix (Keystonea) A.M. Clark, 1967. 24. Macrophiothrix variabilis (Duncan, 1887) SEE. Clark, 1968: 308; Clark & Rowe, 1971: 115; Hoggett, 1991: 1138; Hoggett, 1992: 218; Rowe & Gates, 1995: 416. MATERIAL. 810206A/4 (1). COLLECTION SITES. Negombo, Sri Lanka. HABITAT AND DEPTH. Coral / rock, 5 m. 25. Macrophiothrix virgata (Lyman, 1861) SEE. Clark & Rowe, 1971: 86; 113 (as Ophiothrix (Placophio- thrix) virgata); Hoggett, 1992: 236. MATERIAL. 810423D/2 (1). COLLECTION SITES. Ug Bau, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral reef; 2—8 m. REMARKS. See remarks under Macrophiothrix nereidina. 26. Ophiogymna pellicula (Duncan, 1876) SEE. Clark & Rowe, 1971: 84; 117; Clark & Courtman Stock, 1976; 140 (as O. fulgens); Rowe & Gates, 1995: 417. 810504B/2 (1). Rubiah, Pula Wé, Sumatra. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. Soft coral; 10 m. REMARKS. The single specimen has a d.d. = 2.7 mm, a.l. = c. 20 mm. The disc is mottled cream and pink, and the arms are banded with wide pink and narrow cream bands. An irregular longitudinal line of cream spots is evident along the dorsal midline of the arms. The disc is covered (except for the radial shields) with minute, A.R.G. PRICE AND F.W.E. ROWE pointed granules with larger, conical spines interradially towards the edge of the disc. Clark & Courtman Stock (1976) include Placophiothrix phrixa H.L. Clark as a synonym of O. fulgens (Koehler) which in turn is included in the synonymy of O. pellicula by Rowe (in Rowe & Gates, 1995). The species therefore appears to to be distributed from the Gulf of Aden to the Indo-Malay region and the NW coast of Australia in depths of 10-116 m. 27. Ophiopteron elegans Ludwig, 1888 SEE. Clark & Rowe, 1971: 84; 115; Rowe & Gates, 1995: 419. MATERIAL. 810428D/3e (2), 810428D/5 (8). COLLECTION SITES. Ug Tapa Gadja, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral reef, subtidal rock/coral; 15 m. Family OPHIOCOMIDAE 28. Ophiarthrum pictum Miller & Troschel, 1842 SEE. Clark & Rowe, 1971: 86; 121; Rowe & Gates, 1995: 385. 810502H/1 (1). E Klah, Pula Wé, Sumatra. Subtidal rock, 2m. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. 29. Ophiocomella sexradia (Duncan, 1887) SEE. Clark & Rowe, 1971: 86; 118; Devaney, 1974: 162; Cherbonnier & Guille, 1978: 179: Rowe & Gates, 1995: 389. 81042D8/3d (1). Ug Tapa Gadja, Pula Wé, Sumatra. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. Coral reef; 15 m. REMARKS. The single specimen from Pula Wé measures d.d. = 3 mm; a.l. = 10+ mm (broken near tip). With the exception that the uppermost of the 4 arm spines is distinctly longer than the lower ones, the character separating Ophiomastix sexradiata A.H. Clark 1952 (known only from its type locality: Bikini Atoll, Marshall Is, SW Pacific) from Ophiocomella sexradia (Duncan)(identified throughout the Indo-West Pacific region and possibly tropicopolitan) in Clark & Rowe’s (1971) key, all other skeletal characters of the present specimen accord with those described as fitting O. sexradia (note 65, p. 118) by A.M. Clark. Cherbonnier & Guille (1978), following their study of Malagasy material, concur with the com- ments expressed by A.M. Clark (in Clark & Rowe, 1971) and tentatively consider Ophiomastix sexradiata to be conspecific with Ophiocomella sexradia simultaneously agreeing with A.M. Clark that the status of the genus Ophiocomella as distinct from Ophio- coma remains doubtful. Although the present specimen does nothing to clarify the generic status of Ophiocomella, it does support strongly the view that the two nominal species are conspecific and confirm the synonymy proposed by Cherbonnier & Guille (1978). 30. Ophiocoma dentata Miiller & Troschel, 1842 SEE. Devaney, 1970: 13; Clark & Rowe, 1971: 86; 119; Rowe & Gates, 1995: 386. MATERIAL. 810502H/2b (1). INDIAN OCEAN ECHINODERMS COLLECTION SITES. E Klah, Pula Wé, Sumatra. HABITAT AND DEPTH. Subtidal rock, 2m. REMARKS. This single specimen (d.d. c. 11.3 mm, distorted) exhibits two of the described colour forms for the species. At the centre of the dorsal surface of the disc is a cream spot (c. 1.1 mm diameter). This is surrounded by an irregular ring (c. 2.2 mm wide) which is uniformly dusky/grey with darker spots. The remainder of the disc dorsally and ventrally is reticulated dusky/grey on a cream background. 31. Ophiocoma erinaceus Miiller & Troschel, 1842 SEE. Clark & Rowe, 1971: 114;119; Clark & Courtman Stock, 1976: 173; Sloan et al, 1979: 106; Bussarawit & Rowe, 1985: 1 (as O. similanensis n. sp.); Rowe & Gates, 1995: 387. MATERIAL. 801212A/3 (1), 810422B/3 (10), 810427B/1 (1), 810427D/5 (1), 810428C/6 (2 juveniles), 810428E/5 (1 juvenile), 810430A/3 (2), 810501F/1 (1), 810501G/5 (3), 810501G/6 (2), 810501K/1 (2). COLLECTION SITES. Chetlat, Lakshadweep (Laccadive) Islands; Ug Seukundo, Ug Bau, Lho Pria Laot, Ug Murung, Ug Tapa Gadja, Pula Wé, Sumatra. HABITAT AND DEPTH. subtidal rock; 2-25 m. REMARKS. This is the commonest species of Ophiocoma col- lected. The collection comprises some 26 specimens, ranging in size from d.d. = 3.6—22.2 mm, which show clearly both colour changes and development of disc granulation with growth. Juveniles up to d.d. = c. S mm bear no granules and are usually marked radially across each radial shield with acream line, as described by Bussarawit & Rowe (1985) for their new species O. similanensis. By d.d. = 5.7 mm granules are developed at the centre of the disc and along 10 radiating lines to the edge of the disc where an irregular line of granules is developed around the periphery joining these radiating lines and thus leaving bare the dorsal interradial and radial portions of the disc. By d.d. = c. 11 mm granules are developed over the interradial but not radial regions of the disc, but granules are still not developed ventrally. By d.d. = 12.5 mm granules cover the whole surface of the disc except for the radial shields which remain bare, while granules begin to extend in a wedge shape, on the ventral side of the disc. This arrangement may remain in specimens up to d.d. = 14 mm but generally from about d.d. = > 13 mm the radial shields become covered by granules. In specimens up to d.d. = 12.5 mm some central and peripheral granules may be more prominent by their slightly more elongate shape, but in larger specimens granules are more evenly rounded and more or less evenly sized. The cream colour pattern disappears with increased d.d. and is absent in speci- mens with d.d. > 11 mm. It is very clear that Ophiocoma similanensis Bussarawit & Rowe, 1985 is based on juvenile specimens of O. erinaceus, to the syn- onymy of which O. similanensis is herein committed. Coral reef, coral conglomerate, coral rubble, 32. Ophiocoma pica Miiller & Troschel SEE. Devaney, 1970: 25; Clark & Rowe, 1971: 86; 118; Clark & Courtman Stock, 1976: 173; Sloan et al, 1979: 106; Rowe & Gates, 1995: 387. MATERIAL. 801212A/3 (1). COLLECTION SITES. Chetlat, Lakshadweep (Laccadive) islands. 77 HABITAT AND DEPTH. Coral reef; 20 m. 33. Ophiocoma pusilla (Brock, 1888) SEE. Devaney, 1970: 25; Clark & Rowe, 1971: 86; 118; Clark & Courtman Stock, 1976: 174; Sloan et al, 1979: 106; Rowe & Gates, 1995: 388. MATERIAL. 810422E/4 (1), 810425C/2 (1), 810430A/21c (1), 810501E/3 (1), 810501K/4 (1). COLLECTION SITES. Pula Wé, Sumatra. N Klah island, Sabang Bay, Ug Seukundo, HABITAT AND DEPTH. Coral/sand, coral conglomerate, coral reef; 2-10 m. REMARKS. The 5 specimens range in size from d.d. = 3—7.5 mm. The characteristic, enlarged, tissue-covered arm spines (see Clark & Rowe, 1971) appear on specimens from d.d. > 5 mm. 34. Ophiomastix annulosa (Lamarck, 1816) SEE. Clark & Rowe, 1971: 86; Rowe & Gates, 1995: 390. 810123A/3 (1), 810212A/3 (2), 810213A/4 (1). COLLECTION SITES. Kakoni rocks, Pigeon Island & Unawatuna, Galle, Tangalla, Sri Lanka. MATERIAL. HABITAT AND DEPTH. rock; 3-10 m. Coral reef, subtidal rock/coral, subtidal 35. Ophiomastix caryophyllata Liitken, 1869 SEE. Clark & Rowe, 1971: 86; 120; Cherbonnier & Guille, 1978: 185; Rowe & Gates, 1995: 390. MATERIAL. 810425C/1 (2), 810428C/7 ('/,), 810430A/21b (2). COLLECTION SITES. Wé, Sumatra E Sabang Bay, Ug Bau, Ug Seukundo, Pula HABITAT AND DEPTH. Coral reef, coral/rock; 3—10 m. Family OPHIONEREIDAE 36. Ophionereis dubia (Miiller & Troschel, 1842) SEE. Clark & Rowe, 1971: 122; Clark & Courtman, 1976: 179; Price, 1983: 67; Rowe & Gates, 1995: 408. 810502D/5 (1). E Klah, Pula Wé, Sumatra. Subtidal rock/sand; 10 m. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. 37. Ophionereis fusca Brock, 1888 SEE. Clark, A.M. 1953: 69; 78; Clark & Rowe, 1971: 88; 122; Rowe & Gates, 1995: 408. 810421B/2 (1). Nr. Seukundo, Pula Wé, Sumatra. Subtidal sand; 10-20 m. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. 78 Family OPHIODERMATIDAE 38. Cryptopelta granulifera H.L. Clark, 1909 SEE. Clark & Rowe, 1971: 88; 128; Rowe & Gates, 1995: 394. MATERIAL. 801212B/1 (1). COLLECTION SITES. Chetlat, Lakshadweep (Laccadive) Islands. HABITAT AND DEPTH. Coral rubble; 8 m. REMARKS. Originally described from Mauritius. Rowe & Gates (1995) describe the distribution as including tropical Australia, the Indo-Malayan region and Philippine Islands. The specimen is iden- tified here from the Laccadive Islands for the first time. 39. Ophiarachna affinis Liitken, 1869 SEE. Clark & Rowe, 1971: 88; 123; Sloan et al., 1979: 111; Rowe & Gates, 1995: 395. MATERIAL. 810425C/la,b (1). COLLECTION SITES. E. Sabang Bay, Pula Wé, Sumatra. HABITAT AND DEPTH. Coral conglomerate; 3—6 m. REMARKS. A.M. Clark (in Clark & Rowe, 1971: Note 83, p. 123) describes in detail colour variation in Ophiarachna affinis and O. mauritiensis de Loriol, concluding that specific distinction between the two is difficult to make. In the present specimens with d.d. = 22 mm, the disc is uniformly brownish-grey and the dorsal side of the arms has a broad longitudinal central dusky band either side of which is a narrower pale band, the 3 bands being demarcated by 4 irregular, very narrow longitudinal dark bands. This corresponds to A.M. Clark’s form C colour pattern. If O. affinis and O. mauriti- ensis are conspecific the species is clearly widely distributed in the Indo-West Pacific region. 40. Ophiarachna robillardi de Loriol, 1893 SEE. Clark & Rowe, 1971: 88; 123. 810126B/4 (1), 810213A/3 (2). Galle, Tangalla, Sri Lanka. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. Coral reef, 3—5 m. REMARKS. This is a significant extension of range for this species described from Mauritius. The species is recorded as having 5 arm spines (H.L. Clark, 1909; size not recorded) but the present 3 specimens have 7—9 arm spines at d.d. = 21.5 mm; 9-10 arm spines at d.d. 31.5 mm and 10-11 arm spines at d.d. = 36.5 mm. 41. Ophiochaeta hirsuta Liitken, 1869 SEE. Clark & Rowe, 1971: 88; 127; Sloan et al, 1979: 115; Rowe & Gates, 1995 398. 801212B/1 (1), 810425C/2 (1). COLLECTION SITES. Chetlat, Lakshadweep (Laccadive) Islands; E. Sabang Bay, Pula Wé, Sumatra. Coral rubble, 3—8 m. MATERIAL. HABITAT AND DEPTH. REMARKS. Sloan et al. (1979) concluded that variation in the A.R.G. PRICE AND F.W.E. ROWE occurrence of spinelets on the discs of 4 specimens from Aldabra, western Indian Ocean and 2 specimens from Palau in the western Pacific Ocean which they examined suggested that Ophiochaeta boschmai A.H. Clark, 1964 is a synonym of Ophiochaeta hirsuta Liitken, 1869. They pointed out that Cherbonnier & Guille,1978, had described a new species, O. crinita, based on a single specimen, from Madagascar, but did not comment further. In the present collection the specimen from the Lakshadweep Islands accords with the description of boschmai in that the disc is granule-covered dorsally but bears spinelets on its ventral surface. The specimen from Pula Wé, on the other hand, accords with the description of crinita in that the disc is covered dorsally and ventrally by elongate spines. Considering the comments by Sloan et al. (1979), the two specimens reported herein are referrred to O. hirsuta, with the implication that O.crinita Cherbonnier & Guille should also be referred to the synonymy on the basis that it exhibits the extreme spiny form of O. hirsuta. 42. Ophiodyscrita instratus (Murakami, 1944) n. comb. SEE. Murakami, 1944: 272 (as Ophiostegastus instratus); A.M.Clark, 1968: 320 (as Ophiostegastus instratus; discussion) 810124A/4 (1). Ala Gala, Galle, Sri Lanka. Subtidal rock, 10-15 m. MATERIAL. COLLECTION SITES. HABITAT AND DEPTH. REMARKS. This specimen, apart from its smaller size and fewer naked disc plates, accords so well with Murakami’s (1944) descrip- tion of Ophiostegastus instratus that its identity is in no doubt. The species is, however, transferred to the genus Ophiodyscrita H.L. Clark, 1938 (type-species O. acosmeta H.L. Clark), with Ophiostegatus Murakami, 1944 (of which instratus is the type- species) reduced to a junior synonym of Ophiodyscrita. The distinctness of two genera has been questioned by A.M. Clark (1968) and Guille & Vadon (1985) on the grounds of variation of granulation with increased specimen size. Tabulation of measure- ments (Table 1) taken from original species descriptions and similar details of the specimens from Sri Lanka, shows an interesting picture. From this table it becomes apparent that only two species can be recognised: a) Ophiodyscrita instratus (Murakami, 1943)(d.d. =7 mm) of which the larger Ophiostegastus novaecaledoniae Guille & Vadon (d.d. = 9-11 mm) is a synonym, being an extreme form of instratus in which many disc plates, including the radial shields, have become prominent (convex) and naked of granules; this species possesses supplementary oral shields (granule covered in small specimens < 7 mm d.d.) and b) O. acosmeta H.L. Clark (d.d. = 5 mm) with which O. pacifica (Murakami, 1943)(d.d. 4 mm) and Ophiostegastus compsus A.M. Clark (1968) type locality Bahrain (d.d. = 8-10.5 mm) appear to be conspecific. O. acosmeta has an even covering of granules over the disc which are gradually lost only from the oral shields (as in the type of acosmeta; d.d. = 5 mm) and adoral plates (as in the type series of compsus; d.d. = 8—10.5 mm; though A.M. Clark (1968) does note that the largest paratype of compsus (d.d. = 10.5 mm) has a small bare patch dorsally at the base of 4 of the arms). Supplementary oral shields are absent from compsus, according to A.M. Clark, and are not recorded for either acosmeta or pacifica. In both instratus and acosmeta, as recognised herein, it is clear that arm spine number increases with size. There is clearly insufficient justification for recognising Ophiodyscrita and Ophiostegastus as separate genera on the basis of the extent of disc granulation, for it is clear (see Clark & Rowe, 1971) that such differences occur between species included within INDIAN OCEAN ECHINODERMS 79 Table 1. Details of species Ophiodyscrita acosmeta H.L. Clark* and O. instratus (Murakami)* Taxon d.d.(mm)_ a.sp. l.a.sp. S.0.S. Granulation (disc) Ophiocryptus* 4.00 6-5 1/3 seg. -? Complete cover dorsal and ventral pacificus Murakami, 1943 Ophiodyscrita* 5.0 8(7) 1/2 seg. -? Complete cover dorsal and ventral except 2 oral shields (Clark & Rowe acosmeta H.L. Clark, 1938 (1971: 135) Sindbad spec.* 5.3 6-5 <1/2 seg. +(granule Complete cover dorsal and ventral except radial plate at base of deach arm, covered each mid marginal plate and ventrally, each of the oral shields Ophiostegastus* 7.00 7 1/3 seg. +(naked) | Complete except 3 plates at base of each arm; each mid marginal; each oral instratus Murakami, 1944 shield and supplementary oral shield Ophiostegastus* 8-10.5 9 on 6: We”

i SA; ASME A nner, 7, > ne —~ ! TE Le a} — os wh ‘ a \\ eX, ae i ll SO" == a S77 Fig. 7. Neocyclops (Protoneocyclops) mediterraneus (Kiefer, 1960), adult male swimming legs, posterior view. A, leg 1; B, leg 2; C, leg 3; D, leg 4. patches of tiny denticles on segment, as figured. Palp comprising coxobasis with | spinulate spine and 2 setae distally and | seta (representing exopod) implanted on outer margin, and 1-segmented endopod bearing 3 setae (obscured in Fig. 6D). Maxilla (Fig. 6E) 4-segmented, powerfully developed. Praecoxa and coxa separate. Praecoxa with single, distal endite armed with 2 elements. Proximal coxal endite represented by single seta; distal coxal endite discrete, armed with 1 spine fused to endite and ornamented with 2 strong spinules, and | pectinate spine. Basis with endite bearing 2 stout pectinate elements, one fused to segment, plus reduced pinnate seta. Endopod 1-segmented, bearing 3 stout pecti- nate elements plus 2 reduced, unequal setae. Maxilliped (Fig. 6F) somewhat reduced in size, 4-segmented. Syncoxa bearing 2 weakly developed endites with spine formula 2,1. Basis with 2 distal setae on inner margin; secondary ornamen- tation of spinules and setules on segment as figured. Endopod 2-segmented, setal formula 2,3. Ornamentation on spines and setae of maxilliped as figured; setae on distal endopodal segment naked. Swimming legs 1 to 4 (Fig. 7) biramous, both rami 3-segmented, except leg 4 with 2-segmented endopod; distal endopodal segment 92 subdivided by posterior surface suture marking plane of fusion between second and third segments. Legs subequal in size except first somewhat reduced. Intercoxal sclerites lacking ornamentation. Legs richly ornamented with spinules, setules and denticles, as figured. Armature as follows: Coxa Basis Exopod Endopod Leg | 0-1 1-1 I-1;I-1;0L1,4 0-1;0—2;L,1+1,3 Leg 2 0-1 1-0 I-1;J-1;01,1,5 0-1;0—2;1, 11,3 Leg 3 0-1 1-0 I-1;I-1;01,1,5 0-1;0—2;I, 11,3 Leg 4 0-1 1-0 -1;-1;0L11V 0-1;1,,0,0+1 Spines on legs | and 2 adorned with spinules, those on leg 3 flanged with serrate hyaline frill. Outer spines on exopod and outer and distal spines on endopod of leg 4 ornamented with serrate hyaline frill; inner margin setae on both rami modified, spine-like, ornamented with short pinnules proximally and serrate membrane distally. Fifth legs (Fig. 5F) 4-segmented, joined by smooth intercoxal sclerite. Coxa and basis separate, coxa unarmed, basis bearing plumose seta on outer margin. First exopodal segment elongate, about as long as coxa and basis combined, outer margin with subdistal spine flanged with serrated hyaline frill; spinous process just anterior to insertion point of spine; flanged spine longer than segment; inner margin of segment bearing | distal spine adorned with sparse setules and about as long as segment. Distal margin of second exopodal segment bearing | seta flanked by 2 spines flanged with serrate hyaline frill; spinous process just proximal to insertion point of outer spine; outer spine slightly longer than inner, and longer than first exopod segment; inner spine about as long as first endopod segment; seta shorter than spines. Secondary ornamenta- tion on fifth leg segments as figured. REMARKS. The genus Neocyclops Gurney, 1927 contains 15 spe- cies distributed in coastal waters of the Northeast and Tropical Atlantic (including the Caribbean), the Mediterranean, the Black and Red Seas, the Indian Ocean, as well as the Pacific (Papua New Guinea) (Petkovski, 1986; Fiers, 1986; Pesce & Galassi, 1993; Lotufo & Rocha, 1993; Rocha, 1995). Petkovski (1986) has split the genus into two subgenera according to the number of exopodal segments of the male fifth legs. The subgenus Neocyclops, charac- terized by a 3-segmented male leg 5, embraces the following species: N. medius Herbst, 1955, N. vicinus (Herbst, 1955), N. affinis (Plesa, 1961), N. salinarum (Gurney, 1927) and N. remanei (Herbst, 1952). The subgenus Protoneocyclops, with 4-segmented male fifth legs, comprises P. stocki Pesce, 1985, P. geltrudeae Pesce & Galassi, 1993, P. papuensis Fiers, 1986, P. mediterraneus (Kiefer, 1960), P. herbsti Petkovski, 1986, P. wellsi Petkovski, 1986 and P. ferrarii Rocha, 1995. This subgenus displays the so-called full Tethyan pattern of distribution (Stock, 1993), i.e., circum-tropical in the entire region of the former Tethys Sea. Three other species, viz. N. improvisus Plesa, 1973 from Cuba, and N. magnus (Sewell, 1949) and N. parvus (Sewell, 1949) from islands in the Indian Ocean, cannot be assigned to either subgenus as their males are unknown. Three representatives of the genus are known so far from the Mediterranean region. Neocyclops (N.) salinarum, originally de- scribed from the Suez Canal, was reported also from the Camargue (South France) and the Sirbonian lagoon (Mediteranean coast of Sinai) (Gurney, 1927a; 1927b;Aguesse & Dussart, 1956; Por, 1973). As Petkovski (1986) pointed out, the identity of the French popula- tion needs to be confirmed. Similarly the single copepodid from the D. JAUME AND G.A. BOXSHALL Andaman Islands (Indian Ocean), assigned by Sewell (1949) to this species, should be reexamined. Neocyclops (N.) vicinus, a species distributed along the coasts of Brazil and the Lesser Antilles (Pesce & Galassi, 1993; Lotufo & Rocha, 1993), has been also reported from the Black Sea (as Eurycyclops remanei vicinus) by Plesa (1963) and Monchenko (1975). As pointed out by Lotufo & Rocha (1993), this record is dubious since their material seems more closely related to N. (N.) remanei than to N. (N,) vicinus. The single representative of the subgenus Protoneocyclops in Mediterranean waters is Neocyclops (P.) mediterraneus, originally described by Kiefer (1960) as Pareuryte mediterranea from an anchihaline cave on Menorca (Balearic Islands). Later, Pesce & Galassi (1987) reported it from an anchihaline cave in Southern Italy. Plesa (1981) cited the same species from Cuba, but this record has been reassigned by Petkovski (1986) to N. (N.) stocki, a taxon widespread in the Caribbean region (Pesce & Galassi, 1993). The Neocyclops from Mallorca has been identified on the basis of the 4-segmented condition of the male fifth legs and the relative lengths of the armature elements on this leg. Mallorca is also close to the type-locality of the species (Menorca). Other characters could not be checked against Kiefer’s (1960) original description since this contained only 5 drawings (viz. female anal somite and caudal rami, distal segment of endopod of female leg 4; fifth leg of both sexes, and genital operculum of male). In addition, Kiefer did not designate types for the species. Pesce & Galassi (1987) had only 2 females at their disposal for their supplementary description. A differential diagnosis of Neocyclops (Protoneocyclops) mediterraneus (Kiefer, 1960) can be constructed based on charac- ters of the male fifth leg. It differs from N. (P.) geltrudeae Pesce & Galassi (1993) from Curacao (Antilles) in the number of armature elements on the distal segment (3, compared to 4 inN. (P.) geltrudeae). Differences from N. (P.) papuensis Fiers, 1986 from New Guinea and N. (P.) ferrarii Rocha, 1995 from Brazil involve the relative lengths of the spines on the distal segment (the inner spine is clearly longer than the outer in both these species whereas in N. (P.) mediterraneus the outer spine is subsimilar, slightly longer than the inner). Differences from N. (P.) herbsti Petkovski (1986) from the Red Sea, and N. (P.) stocki Pesce, 1985 from the Caribbean, are based on the relative lengths of the flanged spines on the 2 distal segments of leg 5 (these are clearly shorter than the first exopodal segment whereas in N. (P.) mediterraneus they are longer than the segment). In addition, in NV. (P.) herbsti the armature element on the inner margin of the first exopodal segment is a plumose seta, whereas in WN. (P.) mediterraneus it is a thick spine. Differences from N. (P.) wellsi Petkovski (1986) from Mozambique lie only in the nature of the armature element on the inner margin of the first exopodal segment, which is also a seta in this species instead of a thick spine. Subfamily EURYTEINAE Monchenko, 1975 Genus Euryte Philippi, 1843 Euryte longicauda Philippi, 1843 emend. Giesbrecht, 1900 (Figs 8-11) MATERIAL EXAMINED. Cova de na Barxa (Capdepera). UTM coor- dinates: 539.30; 4393.10. Topography in Andrews et al. (1989): Two adult females, 1 adult male, and 1 copepodid (BMNH 1995. 1323— 1326). Collected by authors, 3 April 1995. — Cova de na Mitjana (Capdepera): 19 adult males, 7 adult females, and 5 CYCLOPOIDS FROM LITTORAL CAVES 93 0125mm 0.05 mm Fig. 8. Euryte longicauda Philippi, 1843, adult male. A, body, dorsal; B, lateral; C, detail of rostral plate; D, genital and first abdominal somites, ventral; E, same, lateral; F, anal somite and caudal rami, dorsal; G, antennule; H, fifth leg. copepodids (BMNH 1995. 1313-1322). Collected by authors, 1 (BMNH 1995. 1327). Collected by D. Jaume, 25 May 1994. April 1995. — Es Secret des Moix (Manacor). Coordinates: 523.69; ADULT MALE. Body (Figs 8A, B) cyclopiform, up to 0.61 mmlong, 4365.53. Topography in Ginés et al. (1975): One adult female —_ body surface completely covered by tiny cuticular granulations. 94 XN \ KN D. JAUME AND G.A. BOXSHALL Fig. 9. Euryte longicauda Philippi, 1843, adult male. A, antenna; B, mandible; C, maxillule praecoxal arthrite; D, maxillulary palp; E, maxilla; F, maxilliped. Prosome about 1.4 times longer than urosome, comprising cephalosome plus 4 free pedigerous somites; first pedigerous somite completely concealed beneath posterior extension of cephalosome, with lateral margins weakly sclerotized; second to fourth somites with evenly rounded posterolateral corners. Ros- trum (Fig. 8C) fused at base, well developed, subtriangular in frontal view. Urosome 6-segmented; first abdominal somite with pointed posterolateral angles; entire hyaline frill adorning posterodorsal margin. Genital somite (Figs 8D,E) symmetrical, laterally expanded, with entire hyaline frill around posterodorsal margin; pair of gonopores opening ventrally at posterior border of somite; opercular flaps each armed with 1 inner flanged spine plus 2 outer setae. Third to fifth urosome somites subequal, narrower than genital somite, with entire hyaline frill adorning posterior margin. Anal somite (Fig. 8F) about same size as preceding somites; smooth anal operculum present at one third of distance along somite; serrate hyaline frill around posterolateral margins of somite. Caudal rami (Fig. 8F) of variable length, from 4.4 to 6.4 times longer than wide, slightly divergent; distal part slightly wider; armature consisting of 6 setae; seta II located subdistally. Antennules (Fig. 8G) 16-segmented, symmetrical, digeniculate with geniculations between segments homologous with ancestral segments XV and XVI (10 and 11), and segments XX and XXI (14 and 15). Segment 10 cup-shaped, forming sheath around proximal half of segment 11. Segmental fusion pattern and armature as follows: Segment | (corresponding to fused ancestral segments I to V), 8 setae + 3 aesthetascs; segment 2 (corresponding to fused ancestral segments VI and VII), 4 setae; segment 3 (VIII), 2 setae; segment 4 (IX), 2 + aesthetasc; segments 5 to 8 (X to XIII), 2 setae each; segment 9 (XIV), 2 + aesthetasc; segment 10 (XV), 2 setae; segment 11 (XVI), 2 + aesthetasc; segment 12 (XVII), 1 short denticulate spine and | seta; segment 13 (XVIII), 1 short denticulate spine, 1 seta + aesthetasc; segment 14 (fused ancestral segments XIX and XX), 1 short denticulate spine, 1 modified flattened spine, CYCLOPOIDS FROM LITTORAL CAVES OS H 4 ry a i i\ 4 WA AY AY Fig. 10. Euryte longicauda Philippi, 1843, adult male swimming legs, posterior view. A, leg 1; B, leg 2; C, leg 3; D, leg 4. 1 seta + minute aesthetasc; segment 15 (fused ancestral segments XXI to XXIII), 2 modified flattened spines, 1 seta + aesthetasc; segment 16 (fused segments XXIV to XXVIII), 11 setae + 2 aesthetascs. Antenna (Fig. 9A) 4-segmented. First segment representing par- tially fused coxa and basis, armed with 2 inner basal setae distally, and 1 outer seta representing exopod; patch of setules present midway along outer margin of segment. Endopod 3-segmented; first segment about as long as coxa and basis combined, armed with 1 seta at three-quarters of distance along inner margin; outer margin ornamented with setules. Segments 2 and 3 subsimilar in size, each about half length of segment 1. Segment 2 armed with 2 lateral and 3 distal setae, one of latter (seta VIII in scheme of Boxshall & Evstigneeva, 1994) claw-like, along inner margin. Segment 3 armed with 7 distal setae, one claw-like; outer margin with 2 rows of setules, as figured. Mandible (Fig. 9B) with large coxal gnathobase bearing 11 unequal, sharp blades, plus 2 dorsal spines; outer dorsal spine spinulate; transverse row of 6 thin spinules located adjacent to cutting edge. Palp reduced to knob bearing 3 setae. 96 Maxillule with praecoxal arthrite (Fig. 9C) well developed, armed distally with 4 stout, denticulate spines, plus 6 more proximal elements, ranging from a tiny seta to a thick denticulate spine. Palp (Fig. 9D) comprising coxobasis with medial gnathobase-like struc- ture and minute endopodal segment bearing 2 setae; distal margin of coxobasal gnathobase provided with 9 irregular blades; coxobasis with 2 setae located subapically on dorsal margin and single seta, representing exopod, located proximally on distal surface. Maxilla (Fig. 9E) well developed, 4-segmented. Praecoxa and coxa incompletely separate. Praecoxa naked, lacking endites. Coxa with proximal endite represented by single seta; distal endite power- fully developed, bearing 2 stout, spinulate spines, proximal spine bearing single, conspicuous strong spinule on outer margin and row of thinner spinules on inner margin. Basis with endite bearing 3 unequal, claw-like setae. Endopod |-segmented, armed with total of 3 stout spine-like setae, 1 naked seta and | very reduced seta. Maxilliped (Fig. 9F) 5-segmented, prehensile. Syncoxa bearing 2 weakly developed endites provided with single seta each. Basis with inner margin covered by patch of setules and single seta positioned distally. Endopod 3-segmented, first segment short, unarmed; sec- ond segment elongate, inner margin covered by patch of setules, armed with 2 setae laterally; small distal segment with 2 stout, curved claws plus 2 accessory setae. Swimming legs | to 4 (Fig. 10) biramous, both rami 3-segmented. Legs subequal in size except first somewhat smaller. Intercoxal sclerites lacking ornamentation and getting progressively narrower from legs | to 4. All spines on segments flanged bilaterally with serrate hyaline frill except distalmost spine on exopod of leg 1, which is flanged with frill on outer side only, inner side adorned with row of setules. Secondary ornamentation and pore pattern on seg- ments as figured; pores on coxa and basis possibly overlooked. Armature as follows: Coxa Basis Exopod Endopod Leg 1 0-1 1-1 I-1;I-1;0L,1,4 0—1;0-2;I-HI Leg 2 0-1 1-0 I-1;I-1;01L1.0V+1 0-1;0—2;I-1-Il1 Leg 3 0-1 1-0 I-1;I-1;0,1,V 0-1;0—2;I-I-Il Leg 4 0-1 1-0 I-1;I-1;10,1,V O—1;0—-II;I--II Fifth legs (Fig. 8H) uniramous, 3-segmented, joined by smooth intercoxal sclerite. Coxa and -basis separate, former naked, latter with single seta on outer margin. Distal segment (exopod) elongate, about 2.5 times as long as wide; armature consisting of flanged spine as long as segment located two-thirds of distance along outer margin, plus 2 flanged spines and single seta on distal margin; distal seta shorter than both spines and segment itself; distal spines located either side of seta, flanged, both clearly longer than segment, inner longer, about 1.5 times as long as segment. Secondary ornamenta- tion of spinules present on outer margin of exopod of some individuals, similar to that figured on female leg 5 (Fig. 11E), not present in figured specimen (Fig. 8H). ADULT FEMALE. Body (Figs 11A, B) up to 0.74 mm long, resem- bling male. Urosome 5-segmented; genital and first abdominal somites partially fused to form genital double-somite. Genital dou- ble-somite (Fig. 11C) symmetrical, subdivided dorsally by partial suture line; single copulatory pore opening mid-ventrally about one-third of distance along somite, connected via copulatory duct to fused seminal receptacles. Paired gonopores located laterally; gonopores covered by opercula, each consisting of lobe projecting dorsally bearing 2 setae and | tiny spine. Tapering soft lobe point- ing posteriorly located at both sides of somite just behind D. JAUME AND G.A. BOXSHALL operculum. Entire hyaline frill present along posterior margin of somite. Antennules (Fig. 11D) 21-segmented, not extending beyond pos- terior margin of cephalosome (Figs 11 A, B), symmetrical. Segmental fusion pattern and armature as follows: Segment | (corresponding to fused ancestral segments I to V), 8 setae; segment 2 (fused ancestral segments VI and VII), 4 setae; segments 3 to 9 (VIII to XIV), 2 setae each; segments 10 to 13 (XV to XVIII), 1 seta each; segment 14 (XIX), naked; segment 15 (XX), 1 seta; segment 16 (XXI), | seta + aesthetasc; segment 17 (XXII), naked; segment 18 (XXIII), 1 seta; segment 19 (XXIV), 2 setae; segment 20 (XXV), 2 + aesthetasc; segment 21 (fused XXVI to XXVIII), 7 + aesthetasc. Segmentation and setation of other cephalosomic appendages and swimming legs | to 4 as in male. Fifth legs (Fig. 11E) resembling those of male, but with shorter exopod, about twice as long as wide; inner distal spine almost twice as long as segment; spine on outer margin clearly longer than segment. Secondary ornamentation of spinules on outer margin of exopod not discernible in some individuals. REMARKS. The genus Euryte typically contains shallow water hyperbenthic species, although Brady (1910) reported the genus from depths of 320 m in the Antarctic and some species have been found living in the interstices of coarse sand, or in association with seaweed or corals. Ten species are currently recognized, distributed worldwide (Gurney, 1927b; Sewell, 1949; Herbst, 1989; Humes, 1991; 1992), with the possible exception of the Pacific coast of South America. Apart from the original contributions by Giesbrecht (1900) and Sars (1913-1918), new species have been described mainly on the basis of a biometric analysis of characters that have otherwise proved to exhibit high intra-populational variability (such as the relative legth of caudal rami), or that may vary significantly in their measurements simply according to the precise angle of obser- vation (such as the relative length of the armature elements on the distal segment of the endopod of leg 4). Such characters are widely used in the two identification keys available for the genus (Vervoort, 1964; Herbst, 1989), and their use has resulted in the false impres- sion of cosmopolitanism of some taxa (viz. E. longicauda and E. robusta Giesbrecht, 1900; see Kiefer (1929) and Sewell (1949)). The type material for most species of Euryte is no longer extant. This hampers the necessary revision of the genus, that could permit the critical reevaluation of all those taxa established on the basis of variable characters. Using material from the type locality of both species (the Gulf of Naples), Giesbrecht (1900) differentiated E. longicauda Philippi, 1843 from E. robusta Giesbrecht, 1900 mainly by the proportions of the caudal rami and by details of the armature of the male antennule. The proportions of the caudal rami of the Mallorcan population overlap the characteristic values for both species given by Giesbrecht (1900). The armature of the male antennule, however, corresponds to that of E. longicauda: the cup-shaped segment 10 carries 2 slender setae, whereas in E. robusta it carries a characteristic robust, S- shaped spine plus a seta. On this basis we have assigned the Euryte from the Mallorcan caves to E. longicauda. The differential diagnosis separating E. longicauda from Mallorca from E. robusta can be completed as follows (see the detailed illustrations of the latter species in Huys & Boxshall, 1991): in E. longicauda the proximal spine on the distal coxal endite of the maxilla of both sexes is armed with a single, strong spinule on one side and a row of thinner spinules on the other side; in E. robusta both sides are armed with thin spinules. Additionally, in E. longicauda there is a transverse dorsal suture midway along the female genital double-somite that seems to be absent in E. robusta. CYCLOPOIDS FROM LITTORAL CAVES 97 Fig. 11. Euryte longicauda Philippi, 1843, adult female. A, body, dorsal; B, lateral; C, genital double-somite, lateral; D, antennule; E, fifth leg. The distribution of E. longicauda apparently encompasses all European coasts from the Black Sea to the Arctic Ocean (Franz- Joseph Land) and the East coast of Greenland (Giesbrecht, 1900; Herbst, 1989) but many of the records of this species are accompa- nied by inadequate descriptions, if any. Geographically remote records from outside the European region, such as those of Gurney (1927b) from the Suez Canal and Samoa, or those of Thomson (1882) (as Thorellia brunnea var. antarctica) from New Zealand, require verification. The body size of the Euryte longicauda from Mallorca falls in the range characteristic of the variety E. longicauda var. minor Scott, 1905, which was elevated, rather inconsistently, to full specific 98 status by Sars (1919-1921). This variety is supposed to inhabit deeper waters and never to occur in the littoral zone (Sars, 1913— 1918; 1919-1921). According to Sars (1913-1918) E. longicauda carries only modi- fied flanged spines on the inner margin of the third exopodal segment of leg 2. In our material the proximalmost element on the inner margin of this segment is a plumose seta (Fig. 10B). However, this may be an observational error by Sars since material of E. longicauda from Raunefjorden in Norway (BMNH 1986.387) and from Scotland (BMNH 1951.8.10.587) in the collections of the Natural History Museum possesses a plumose seta in this position, as in the Mallorcan material. REVIEW OF EURYTE SPECIES The eight remaining species of Euryte are briefly reviewed here, in order to facilitate the identification of representatives of this prob- lematic genus. The review is essentially comparative and emphasises the most robust and reliable characters available in published de- scriptions. E. curticornis Sars, 1913 is characterised by short, 21-segmented female antennules and the shortened third segment of the maxilliped; the curved distal claws on this appendage are also reduced in size and subsimilar in length. These features contrast with the maxilliped of E. longicauda, which is provided with an elongate third segment and with long, unequal distal claws. The distal spines on the third segment of endopod of leg 1 are clearly unequal in length in E. curticornis, whereas in E. longicauda they are about equal. E. longicauda can be distinguished from E. grata Herbst, 1989 and E. verecunda Humes, 1992 by some features of the maxilla and maxilliped. In E. verecunda, the proximal spine on the distal coxal endite of maxilla is adorned on both sides with slender spinules. On the maxilliped, the armature element on the proximal syncoxal endite is a seta in E. longicauda, whereas in E. grata and E. verecunda this endite is represented by a stout spine. E. verecunda differs additionally in the setose condition of the armature elements on the inner margin of the second endopodal segment of leg 4; these elements are flanged spines in E. longicauda. The generic placement of E. verecunda needs verification since, according to Humes (1992), this species displays a 2-segmented condition of leg 5. This is a characteristic of the genus Ancheuryte Herbst, 1989, whereas in Euryte leg 5 is 3-segmented in both sexes. In E. pseudorobusta Vervoort, 1964 two distal setae are present in the outer margin of the antennary coxobasis, whereas there is only 1 seta in E. longicauda. The proximal spine on the distal coxal endite of maxilla has a different armature in the two species, with a row of setules along each side in E. pseudorobusta. Finally, the caudal rami of E. pseudorobusta are short, about as long as the anal segment, and differ significantly from the elongate caudal rami of E. longicauda. Two other species, each described from a single female from the Addu Atoll (Maldives), viz. E. brevicauda Sewell, 1949 and E. sewelli Vervoort, 1964 (= “Euryte sp. of Sewell, 1949) also differ from E. longicauda in their very short caudal rami. The status of E. sewelli Vervoort, 1964 as a distinct species from E. brevicauda is equivocal (Vervoort, 1964; Sewell 1949). The main difference be- tween them is the apparently 18-segmented female antennule in the former species. Unfortunately, Sewell’s (1949) original material is not preserved, thus precluding verification. However, if Sewell’s illustrations are accurate, the 18-segmented antennule, combined with the absence of the inner seta on the proximal segment of exopod of leg 1, can be used as diagnostic characters of this taxon. D. JAUME AND G.A. BOXSHALL E. longicauda differs from E. bellatula Humes, 1991 in the nature of the two armature elements on the inner margin of the second endopodal segment of leg 4; these are flanged spines in the former species, whereas in the latter they are setae. E. bellatula also has the proximal spine on the distal coxal endite of maxilla armed with a row of thin spinules on both sides.As commented above for E. verecunda, the generic placement of E. bellatula must be confirmed due to the apparently 2-segmented condition of the leg 5. The association with corals of the two taxa described by Humes is similar to the life-style of Ancheuryte, a closely related genus characterized by its 2-seg- mented leg 5. The status of E. similis Scott, 1912, originally described from the South Orkneys and never found since, is debatable. Scott pointed out its similarity to E. robusta, and that it appeared ‘. . . to differ in one or two minor points, such as in the armature of the first and fourth pairs of thoracic legs and in the proportional lengths of the abdomi- nal segments’ (Scott, 1912). The differences in the armature of the swimming legs mentioned by Scott in the text do not correspond with his figures. Also, as Sewell (1949) already pointed out, it seems certain that Scott had confused the legs so that his second leg is in reality the fourth, and his fourth leg is either the second or third. In fact, the original description is very superficial and does not permit any conclusion other than that the taxon belongs to Euryte. The only apparent diagnostic features displayed by this taxon could be the lack of an inner seta on both the first endopodal and first exopodal segments of leg 4 (Scott’s leg 2). This is unreliable, however, since the number of armature elements on the swimming legs is a very conservative character at the generic level in the Cyclopidae. In our opinion, given the lack of type material, this taxon should be considered species inquirendum. ACKNOWLEDGEMENTS. We want to thank J. Pons-Moya and G. Pons their support during fieldwork, and Dr Rony Huys and Prof Carlos Eduardo Falavigna da Rocha for their detailed comments and improvements to the manuscript. Contribution to project DGICYT PB91—0055 and EC Training Research Contract ERBCHBICT941306. REFERENCES Aguesse P.C. & Dussart, B.H. 1956. Sur quelques crustacés de Camargue et leur écologie. Vie et Milieu, 7: 481-520. Andrews, J.N., Ginés, A., Ginés, J., Pons-Moya, J., Smart, P.L. & Trias, M. 1989. Noves dades sobre el jaciment paleontologic de la Cova de na Barxa (Capdepera). Endins, 14/15: 17-26. Boxshall, G.A. & Eystigneeva, T.D. 1994. 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An account of the Crustacea of Norway. VII. Copepoda Supplement. 121 pp., 76 pls. Bergen Museum. Schafer, H.W. 1936. Cyclopiniden (Crustacea Copepoda) aus der deutschen Nordsee. Zoologischer Anzeiger, 113: 167-174. Scott, T. 1912. The Entomostraca of the Scottish National Antarctic Expedition. Transactions of the Royal Society of Edinburgh, 18: 521-599, 14 pls. Sewell, R.B.S. 1949. The littoral and semi parasitic Cyclopoida, the Monstrilloida and Notodelphyoida. Scientific Reports of the John Murray Expedition, 7: 117-382, | chart. Stock, J-H. 1993. Some remarkable distribution patterns in stygobiont Amphipoda. Journal of Natural History, 27: 807-819. lliffe, T.M. & Williams, D. 1986. The concept ‘Anchialine’ reconsidered. Stygologia, 2: 90-92. Thomson, G.M. 1882. On the New Zealand Copepoda. Transactions and Proceedings of the New Zealand Institute, 15: 93-116. Trias, M. & Mir, F. 1977. Les coves de la zona de C’an Frasquet — Cala Varques. Endins, 4: 21-42. Vervoort, W. 1964. Free-living Copepoda from Ifaluk Atoll in the Caroline Islands with notes on related species. United States National Museum Bulletin, 236: \- 431. ©. tee" BP tka Saow | ea) ete ee 6 eee 2 @ ye * p—eeoce ae ee oe () << oie 30, fies Tot — Lat C+ fete pet pre fa = 98S) fe Lever be)) Sewlel) sey ) Or ee inca od Af aad et ee ds ee ae! a — ti@) Den dhe aod det : ae tet ‘aw. 210 Cd! 6c0 ee ore tele <<" */° rete e as i % — . a S ! rn { eae chs Clie doo sh. , yok MANET A, . a Snore a =o > o~— leu < 1 fT £ 7 ‘to =" | 6) @e = \ = ( = ~~ ~. 4 ‘aay . by one a o @ =e AQP 10 x i =. = Bull. nat. Hist. Mus. Lond. (Zool.) 62(2): 101-132 Issued 28 November 1996 Studies on the deep-sea Protobranchia (Bivalvia): the family Neilonellidae and the family Nuculanidae. J.A. ALLEN University Marine Biological Station, Millport, Isle of Cumbrae, Scotland, KA28 0OEG H.L. SANDERS The Woods Hole Oceanographic Institution, Massachusetts, 02543, USA CONTENTS SOILED [LS 1S ete emer SN Rg Sees. S es OM aC vids s van cv on cnn Tssnnhnisakctanch eogunsecsupitcas cis exenusiusengech incncedap iogttWarsoeeacennsecpenscisecenses 101 PRIA CRIN LQ) EN cece cee «a este sn eects cne sabia aac dus eat anne voice do aieh sar sovaestidaerststresanavreneneceustpsaanetssennaceeeetiannes vatasgessevseeveseiaeeteceysteanss 101 Es ATMIM UYU NIL eS NLRC A aoe fis chicas can tanec or seep ene gen ok Suits he Coes toe cence Madea sears esr ature ree aeed/swactCeastedetaaeewarasenstheceeteastewsscedettn tude 102 UNUM ELLIGE TES ISI (SEPUICIIZA LO, 11) srecncetitexoeanccacessnersvssccancadvenseeteets cebesthacuevenieesceray sonevads¥=sdenchesavasecksvaceconesrereceaetyaeeene 103 ENING EAI PIS ONL (MEW SPECIES etacear teas dene de asewncauereney asia saz sasaneecovupacnatenancvduertanccerdesscevdabaatevceudddscctusasesiete cuodsessduaadteaeated 107 INU OUELLGIC ON DILLCIGN (DAIS USS SlNne, cern a cetc cae ee cst centres x unacbusteueneenice secbaseen aes hla wah cetavee se ueke nuns stccthesasuutes. odes ceameaberes 108 ALLO MELON ROM CHEW SPECIES) lees ste. cantar te ca aant vaste rer achctxaxcxaaec cnet tate ment cceeeeota caer eactereskamee re caae dan eeescargacessacacnsrentargnassesss 108 seo tA UUW MINGNG UN) ANDY LAC. cy crear ce enya ups nas «APE MATE ERE EN cups onseans Linc receu scooter tamiece cate canteen eetaetenaqaceetet (anet ee Ver spel ate ee ict 111 aA N ARUN ae LE ESSA Fit oes covsarsdeaasszais¥sarsacbstuxasdssaqenesovsosanvsnesTiuasavuddesaaduat dedansnusataes scdessuveabeableteaenaseansusvntUabansiteessecesccar'scceseaas 111 (LE GIAING) ate APO CLD FANNIE (0) Ear Acar ee Soe Ree EA eee ae x ROPE ene oh RR he tee a ee erie 111 EHO ADETEALG (HEMT SDECICS) HS chiten tok fe ste a ccsisreits SrassscvuvssesssuneddsonnenecuaititcceadesiuapcanSunsanansvetsnn'ssuseqiviacedssycsstcesrectaeeecenans 114 STEAL TU TGTISUSU CEA CESILECEE (UD AMUSO) a cc an esi cau sendn anny av nase nc sstalve cac ouve ns uiaiic oa epttaenenemmec van eXes conta Gxon0s eaRSa Nata ctan masts gan ceaeee a ewes 116 TRA GZIOPSUS CEOLIC (DAUM) io, cacestaecadeccevaususssecssacssessaness icsnccscciusexpevuatsnemenesccteterddctecassssaineYehsadssousvssscivsesexe 123 PEGs TIRES LUTON ERISA MMI ONC eee CEE ote UNG SIRE cs vsicc at cdueunoaswe'soRammedane te aaakins cab ones cance veseuxengaccnossamunaeseasetee nacaaeeenans 124 Ea OPRCNCCED COR DER CETIN (ID) AML OU) pcapres. seuteante teatwe vatceee hestavkscuvsvacdsssnevavssesnu dadacobansaraneynesanaavsncvadacsehi veadtossesstusnoseduduansseddananoneas 125 EFOPVERCAIA ALISCLCA (© LAT OWL Oly hemesmanceeee nattes cntdeter ee wesencsacsavesvscecosvnestradedtentsansesusasdastoaseeasssssscensseosonseonentatesctetrusteseunens 127 FORE IAA Cn POUGES Teta fell (TEIN SDEGIOS ads cron raer ate eis vawasenicsnaveviecent'asch voswendsnns suacsbisxaceenestsseabedaivdevvittectsserestoesessacentspincstece 128 AERTS S100 te eee ea tae pete ey ee eee eng PORES gba ac ceeyarenrstceevedchnevndieepewdewarencdewacapesstnld'dtesnsnerdeisavebvecehooveusmstecersecree 130 RKC TOU CES pean ce casntra ss ieee «athe Mae aaa as ass anion xh case ub i atv aasas curse sh 3mm total length) are more posteriorly attenuate than smaller specimens. There is a fair degree of variation in the ratios which is not related to the different populations sampled. Unusually in some samples the length fre- quency histograms are skewed to the right (Fig. 6) and with clearly Length (mm) Fig. 5. Neilonella salicensis. The ratios height to total length (H/TL)(large symbols) and post-umbonal length to total length (PL/TL)(small symbols) plotted against total length to show changes in shell proportions with increasing length. Open circles are specimens from Biogas III station DS 49 West European Basin, closed circles from Sarsia Station S44 West European Basin and closed squares, from Chain 58 station 103 North America Basin. 106 30 220 syJwawn 10 J.A. ALLEN AND H.L. SANDERS LENGTH (mm) Fig. 6. Neilonella salicensis. Length/frequency histogram of a sample taken from Atlantis II station 73 from the North America Basin. marked size groups. It is unclear whether these latter relate to annual settlements or to fortuitous periodic settlements. INTERNAL MORPHOLOGY (Figs 7 & 8) This was one of the few deep-sea species that were kept alive for a few weeks following the processing of the sample. The external drab olive/yellow of the shell is in marked contrast to the spectacularly vivid array of colours of the body organs. The stomach is a bright emerald green, the digestive gland a bright olive green and the gills are bright red. The gill plates are particularly vivid below the frontal cilia and dorso-laterally, in addition the mantle overlying the gills is also red. The margins of the palps are a diffuse pink as too is a band underlying the crest of the inner folds. The red and pink pigments are probably a cytochrome. The blood is not red in colour and probably contains a haemocyanin as do other protobranchs (Taylor, Daven- port and Allen, 1995). Elsewhere the palps are pale yellow and the yellow/pink effect is in marked contrast to the palp proboscides which are pure white. Fig. 7. Neilonella salicensis. Semidiagrammatic view of the internal morphology as seen from the right side. See abbreviations to text-figures on p. 102. Scale = 1mm. The mantle has three marginal folds of which the inner is fused at the posterior end to form the siphon. Fusion is minimal, restricted to the dorsal margin of the siphon (Fig. 8). Ventrally the siphonal margins are unfused as too are the longitudinal ridges that mark the division between the dorsal exhalent and ventral inhalent channels. The gill axes attach to the inner ends of the longitudinal ridges. There is a shallow siphonal embayment and attached to its inner limit on the left or the right side is a siphonal tentacle which in living specimens extends beyond the shell margin at distance equal to a third of the shell length. Ventral to the anterior adductor muscle there is an elongate anterior sense organ, which consists of a flap of tissue derived from the middle sensory fold. A major ciliated rejection tract is present on the inner face of the inner mantle fold. The adductor muscles are relatively small, unequal in size, with the posterior the smaller. The posterior muscle is round in cross-section while the anterior is bean-shaped. The gills, with up to 26 plates, are slung from a horizontal axis extending from the base of the siphon to a point about half way across the body. Individual gill plates are exceptionally elongate for a deep-sea protobranch. The foot is broad and the divided sole has papillate margins, the anterior papillae are the more pronounced. There is a small median papilla present posterior to the aperture to the ‘byssal’ gland. The latter is extremely large. The pedal muscles consist of a pair of broad posterior retractors, one on each side of the hindgut anterior to the posterior adductor, and a series of four pairs of anterior retractors posterior to the anterior adductor. The two inner muscles of the four lie more close together than to the two outer. The palps are relatively large with up to 27 inner ridges depending on the size of the specimen. Each bears a long narrow palp probos- cis. A ciliated rejection tract traverses the lateral face of the foot at the junction of of the muscular and visceral parts and the posterior ventral point of the palp is positioned at the posterior limit of this tract in the living animal. The mouth is set far posterior to the anterior adductor. The oesophagus curves first antero-dorsally to meet the inner face of the anterior adductor then postero-dorsally to open on the anterior face of the stomach. The stomach is large and slung diagonally within the visceral mass. The pedal muscles form a ventral ‘basket’ in which the stomach rests. The stomach, which is similar to that of other DEEP-SEA PROTOBRANCHIA (BIVALVIA) FA Fig. 8. Neilonella salicensis. Detail of internal morphology; a, lateral view from the right side of the stomach and style sac; b, internal view of a dissected gastric shield; c, diagrammatic enlargement of the siphonal region to show the relationship of the parts. See abbreviations to the text-figures p. 102. Scales = 0.5mm (A); 0.1mm (B). protobranchs (Purchon, 1956), is one third lined with a gastric shield dorsally and to the left (Fig.8). The unlined right wall bears very few sorting ridges. The style sac is flask-shaped rather than the more usual conical outline of other protobranchs. The combined mid gut is guarded by minor and major typhlosoles. The hind gut penetrates the foot to a point ventral to the pedal ganglia before taking a course posterior to the stomach and thence to form a loop to the right side of the body. This single loop extends anteriorly as far as the anterior adductor muscle and where it then takes a dorsal course along the margin of the body to the anus. The hind gut has a particularly wide diameter compared with most other deep-sea protobranchs and has a well-marked typhlosole present along its entire length. The diges- tive gland which lies anterior and dorso-lateral to the stomach has three sections each connecting with the stomach via a duct. The apertures of the ducts are ventral, and left latero-ventral to the oesophageal aperture. The nervous system is of a typical protobranch design with elongate pairs of cerebral and visceral ganglia and large ovoid pedal ganglia. These are connected by very stout cerebro-visceral and cerebro-pedal commissures. A statocyst lies dorsal each pedal gan- 107 glion. From visceral ganglia three main nerves pass to the gill, hind gut and mantle/siphon, and from the cerebral ganglia nerves pass to the palps and mantle. The sexes are separate, specimens greater than 4mm total length have gonads. The gonad first develops at the periphery of the visceral mass and as it matures it spreads across the lateral surface of the viscera. On the right side of the body, apart from a small portion postero-dorsal to the loop of the hind gut the gonad does not extend beyond the confines of the of the loop. While different samples show different degrees of maturity, the specimens of each sample appear to be maturing synchronously. The ratio of males to females is approximately 50:50. Neilonella hampsoni new species TYPE SPECIMEN. 1995050. Holotype BMNH 1995049; paratype BMNH TYPE LOCALITY. Atlantis II cruise 31, station 155, Sierra Leone Basin, 00'03.0'S 27'48.0'W, 3730-3783m. MATERIAL: Cruise Sta. Depth No Lat Long Date Gear (m) SIERRA LEONE BASIN Atlantis 11 155 3730-3 00°03.0'S 27°48.0'W 14.2.67 ES 31 3783 J.Charcot DS035150 1 10°59.0'N 45°15.0'W 16.11.77 DS Vema DISTRIBUTION. Anabyssal species, to date only found in the Sierra Leone Basin at depths from 3730m to 5150m. SHELL DESCRIPTION (Figs 9 & 10) Shell robust, oval, wide, ornamented with concentric ridges, straw- coloured periostracum; umbo prominant, anterior to midline (postumbonal length c.60% of total length in large specimens), inward facing; lunule and escutcheon, both well-defined; postero- dorsal margin in lateral view almost straight, slopes relatively steeply from umbo to proximal limit of hinge, rounded angle to posterior margin, anterior and ventral margins form a smooth curve, distally antero-dorsal margin slightly concave then slopes steeply in smooth curve to anterior margin; anterior limit of shell coincides Fig. 9. Neilonella hampsoni. Lateral view of the right valve of the holotype, from Atlantis II station 155 from the Sierra Leone Basin. Scale = 1mm. 108 Fig. 10. Neilonella hampsoni. a, lateral view of the hinge plate of the right valve of a paratype; b, dorsal view of the shell of the holotype. Both specimens taken from Atlantis II station 155 from the Sierra Leone Basin. Scales = Imm. with horizontal midline, posterior limit of shell immediately ventral to mid line; hinge plate stout extending along most of the dorsal shell margin, anterior and posterior tooth series meet below umbo, with faint suggestion of an edentulous space between, 13 posterior and 10 anterior teeth in specimen 3.9mm total length, teeth increase in size distally, teeth chevron-shaped, obtuse, so much so that teeth appear to be a straight line transverse to hinge plate; ligament opisthodetic, external, short, anterior outer layer extremely short, hidden beneath umbo, no resilium. Maximum total length of present specimens is 7.5mm. Apart from N. salicensis, from which it differs in having a shorter, wider shape, and well-marked lunule and escutcheon, the only other protobranch species with which it has some similarity is ‘Leda’ sericea vat ovata Jeffreys 1876 (Jeffreys, 1879). One of us (JAA) has examined specimens of this latter species in the Natural History Museum, London, (BMNH 85 11 5483-84) and find that L. sericea is more ovate, with the dorsal margins much less sloping, a more anteriorly positioned umbo and a much more narrow hinge plate. INTERNAL MORPHOLOGY The morphology is similar to Neilonella salicensis. Such differences that do exist include the adductor muscles, both of which are small, similar in size, but with the posterior oval and the anterior round in cross section. The foot is somewhat smaller but with a moderately large byssal gland with a small, hooked, median papilla posterior to its aperture. Except for the posterior quarter of their length, the margins of the divided foot are finely papillate. There are approxi- mately 20 gill plates and 25 ridges on the palps of a specimen 3.9mm total length. The hind gut makes a simple loop to the right side of the body, it has a wide lumen (0.21mm in diameter) with a single well- defined typhlosole running its entire length. The stomach is large and the mouth lies some distance posterior to the inner wall of the anterior adductor. The kidney extends in a narrow band from the posterior margin of the posterior adductor, anteriorly narrowing over the viscera, and terminating at the posterior edge of the digestive diverticula. J.A. ALLEN AND H.L. SANDERS It is named after our good friend and colleague George Hampson who accompanied us on so many of our cruises and without whom sampling at abyssal depths would not have been the resounding success that it proved to be. Neilonella corpulenta (Dall 1881) TYPE LOCALITY. Blake station off Havana, 823m (station number not recorded but, only station 51, 23°11.0'N 82°21.0'W, is listed as having a depth of 450fm (823m) (Smith, 1888)). TYPE SPECIMEN. Holotype, U.S. National Museum 63169. Cited specimen: BMNH 1995048. Leda (Neilonella) corpulenta Dall, 1881, 125; 1886, 254, pl. 7, figs. la, 1b. Neilonella (N.) corpulenta Laghi 1986, pl.9, figs 1-3. MATERIAL: Cruise Sta Depth No Lat Long Date Gear (m) BRAZIL BASIN Atlantis] 162 1493 1 08°02.2'S 34'03.0'W 19.2.67 ES 31 The type specimen has been examined by us. DISTRIBUTION. An upper slope species previously recorded only from the Gulf of Mexico but here found in the Brazil Basin. It occurs at depths from 347m to 1493m. SHELL DESCRIPTION (Fig. 11) Dall (1881) gave an adequate description which was later (Dall, 1886) augmented by good internal and external lateral views of the shell. The specimen collected from the Brazil basin differs little from the type (Dall, 1881, 1886)(Fig. 11):- Shell elongate, solid, oval, ornamentated with concentric ridges; umbo not particularly large or elevated, somewhat anterior to the mid line; postero-dorsal margin almost straight, slightly upturned posterior to the distal limit of the hinge, then sharply and smoothly curved to posterior margin, ventral margin shallow smooth curve, not posteriorly sinuous, anterior margin smoothly curved, antero- dorsal margin relatively steeply angled, distally slightly raised; hinge plate elongate, relatively wide, hinge teeth chevron-shaped, 9 in anterior and 12 in posterior series; external ligament slightly opisthodetic, short; resilium small ventral to umbo. Dall (1881) states that there are an equal number of teeth in the anterior and posterior series (15), however the type specimen which is larger than the present specimen, has 17 anterior and 20 posterior teeth. The total length of present specimen is 3.1mm. INTERNAL MORPHOLOGY Both adductor muscles are oval in cross section, the anterior is somewhat larger than the posterior but neither is particulaly large. The foot is relatively short with large marginal papillae. The palps are relatively short with 7 broad internal ridges. The gill is also short. The siphonal embayment is shallow and the siphons similar to those described for N. salicensis. The hind gut forms a single loop to the right side of the body and has a typhlosole along its entire length. Neilonella whoii new species TYPE SPECIMEN. 1995053. Holotype BMNH 1995052; paratypes BMNH DEEP-SEA PROTOBRANCHIA (BIVALVIA) Fig. 11. Neilonella corpulenta. a, an external lateral view of the right valve of specimen No 63169 from the USNM and an internal lateral view of the 109 central region of the hinge of the same valve; b, lateral view of the intact shell, from Atlantis II station 162 from the Brazil Basin, and an internal view of the left valve of the same specimen to show detail of the hinge plate. Scales = 1mm. CITED SPECIMEN. BMNH 1995054. TYPE LOCALITY. Chain cruise 50, station 78, North America Ba- sin, 38°00.8'N 69°18.7'W, 3828m. MATERIAL: Cruise Sta Depth No (m) WEST EUROPEAN BASIN Chain 106 323 3356-7 3338 326. )3859) .5 328 4426-6 4435 330 4632 J.Charcot DS20 4226 Polygas DS22 4144 DS23 4734 DS28 4413 J.Charcot CV23 2034 Biogas III DS41 3548 CV27 4023 CV30 4518 53 DS47 4230 2 J.Charcot CV34 4406 1 io) eS = ee DO ND) oo Lat 50°08.3'N 50'04.9'N 50°04.7'N 50°43.5'N 4733.0'N 4734.1'N 46°32.8'N 44°23.8'N 4732.7'N 4728.3'N 4734.2'N 46°32.8'N 44°26.8'N 44°27.2'N Long 13°53.7'W 14°23.8'W 15°44.8'W Date 21.8.72 22.8.72 23.8.72 17°51.7'W 24.8.72 09°36.7'W 09°38.4'W 10°21.0'W 04°47.5'W 08°34.2'W 09°04.2'W 09°32.4'W 10°20.0'W 04°50.7'W 04°49. 1'W 24.10.72 25.10.72 26.10.72 2.11.72 25.8.73 26.8.73 28.8.73 28.8.73 S873 19.2.74 Gear ES ES ES ES DS DS DS DS CV DS CV CV DS CV Biogas IV Cryos Biogas V J.Charcot Biogas VI J.Charcot Incal DS53 4425 DS54 4659 DS56 4050 DS60 3742 DS66 3480 DS75 3250 DS76 4228 CP14 4237 DS78 4706 DS79 4715 CP18 4721 DS81 4715 CP19 4434 DS82 4462 OSO1 2634 DS11 4823 CP11 4823 OS02 4829 OS05 4296 OS06 4316 DS16 4268 WS09 4277 CANARY BASIN Discovery 6711 2988 ow NSH WWW RR We We KS YL OO f 44°30.4'N 46°31.1'N 47°32.7'N 4726.8'N 4728.2'N 4728.1'N 47°34.8'N 47°32.0'N 46°31.2'N 46°30.4'N 46°30.5'N 46°28.3'N 44°24.9'N 44°25.4'N 50°15.2'N 48°18.6'N 48°21.2'N 48°19.1'N 4732.9'N 4727.9'N 4730.3'N 4727.9'N 27 14.9'N 04°56.3'W 10°29.2'W 09'28.2'W 09°07.2'W 09°00.0'W 09°07.8'W 09°33.3'W 09°35.9'W 10°23.8'W 10°27.1'W 10°26.0'W 10°24.6'W 04°51.3'W 04°52.8'W 13°11.0'W 15°12.0'W 15°13.7'W 15°15.5'W 09°34.7'W 09°36.0'W 09°33.4'W 09°34.0'W 15°36.3'W 19.2.74 21.2.74 23.2.74 24.2.74 17.6.74 22.10.74 23.10.74 23.10.74 25.10.74 26.10.74 26.10.74 27.10.74 28.10.74 29.10.74 30.7.76 1.8.76 1.8.76 2.8.76 7.8.76 9.8.76 9.8.76 10.8.76 19.3.68 DS DS DS DS DS DS DS GE DS DS GP DS CP. DS OS DS GP OS OS OS DS WSs ES 110 SIERRA LEONE BASIN Atlantis II 146 2842-2 1039.5'N 1744.5'W 6.2.67 ES 31 2891 147 2934 4 1038.0N 1752.0'W 6.2.67 ES 148 3814 4 1037.0N 1814.0'W 7.2.67 ES 3828 149 3861 1 1030.0'N 1818.0'W 7.2.67 ES GUINEA BASIN J. Charcot DS28 1261 2 04°21.2'N 0435.2'E 7.8.71 DS Walda ANGOLA BASIN Atlantis II 195 3797 46 14°49.0'S 09°56.0'E 19.5.68 ES 42 197 4595 25 1029.0'S 0904.0'E 21.5.68 ES 198 4559- 20 1024.0'S 09°09.0'E 21.5.68 ES 4566 199 3764—- 3 09°49.0'S 1033.0E 22.5.68 ES 3779 200 2644 8 09°43.5'S 1057.0E 22.5.68 ES 2754 NORTH AMERICA BASIN Atlantis II 2 Sis 2 38°05.0'N 6936.0W 22.5.61 AD 264 Atlantis II 64 2886 2 38°46.0'N 7006.0'W 21.8.64 ES 12 YP 2864 9 38°16.0'N 71°47.0'W 24.8.64 ES Chain 50 76 2862 3 39°38.3'N 6757.8'W 29.6.65 ES Vl 3806 752 3800.7'N 69°16.0'W 30.6.65 ES 78 3828 199 3800.8'N 6918.7';W 30.6.65 ES 80 4970 1 34°49.8'N 6634.0'W 2.7.65 ES 85 3834 11503759.2'N 69°26.2'W 5.7.65 ES Atlantis II 124 4862 1 3726.0'N 6359.5'W 22.8.66 ES 24 126 3806 48 3937.0'N 6647.0'W 24.8.66 ES Atlantis II 175 4667- 1 3636.0'N 6829.0'W 28.11.67 ES 40 4693 Chain 106 334 4400 3 40°'42.6'N 4613.8'W 30.8.72 ES 335 3882-5 40°25.3'N 4630.0'W 31.8.72 ES 3919 Knorr 35 340 3264-95 3814.4'N 7020.3'W 24.11.73 ES 3356 BRAZIL BASIN Atlantis II 156 3459 6 00°46.0'S 29°28.0'W 14.2.67 ES 31 GUYANA BASIN Knorr 25 287), 24980 ISelOlOIN 5452) 2\Wie 242 2) ES 4934 288 4417-19 1102.2'N 5505.5'W 25.2.72 ES 4429 291 3859- 43 1006.1'N 55°14.0'W 26.2.72 ES 3868 301 2487— 23 0812.4'‘N 5550.2'W 29.2.72 ES 2500 303 2842- 8 O8'28.8'N 5604.5'W 1.3.72 ES 2853 307 3862-15 12344'N 58°59.3'W 3.3.72 ES 3835 J.Charcot DSO5 5100 3 1046.0N 4240.3'W 19.11.77 DS Biovema ARGENTINE BASIN AtlantisII 242 4382- 1 38°16.9'S S15 Og Wael S347 E'S 60 4402 243 3815- 3 37 36.8'S 52°23.6W 14.3.71 ES 3822 247 5208- 6 43°33.0'S ASS Sell Wieeel-o- lS 5225 256 3906- 8 37 40.9'S 5210S Wee Sales 3917 AS) BR0S= il SBS 52°45.0W_ 26.3.71 ES 3317 DISTRIBUTION. An abyssal species, found widely within temper- ate and tropical latitudes at depths ranging from 2487m to 5223m. J.A. ALLEN AND H.L. SANDERS SHELL DESCRIPTION (Figs 12 & 13) Shell robust, ovate, moderately wide, ornamentated with marked concentric ridges, straw-coloured periostracum; umbos prominant, inwardly facing, clearly anterior of vertical midline in specimens >3.0mm, more central in smaller specimens (post-umbonal length c. 57% of total length); no clearly marked lunule or escutcheon, but some specimens with faint indications; postero-dorsal margin slight concave curve, very slightly angulate opposite limit of hinge plate then steepening to posterior margin, posterior margin may be somewhat flattened particularly in small specimens, ven- tral margin moderately curved joining anterior and antero-dorsal margins in a smooth curve, anterior and posterior limits of shell dorsal to mid-horizontal line; hinge plate broad, continuous, elon- gate, short chevron-shaped hinge teeth, up to 14 in posterior series, 12 in anterior series, numbers varying with size of speci- men, edentulous space below umbo very small; external ligament short, opisthodetic, resilium microscopic, close to shell margin, ventral to umbo. Maximum total length of present specimens is 9.8mm. Neilonella whoii most closely resembles N. salicensis. It can be separated from the latter species by its more rounded shape and greater height. The posterior shell margin is not as acute and the posterior limit of the shell is more dorsal in position as compared with N. salicensis. Furthermore, the post-umbonal length of UN. wholi 1s somewhat longer than in N. salicensis and the hinge plate is not so broad having a smaller ratio of anterior to posterior teeth. We name this species in honour of the Woods Hole Ocenanographic Institution, through whose auspices these studies were carried out. INTERNAL MORPHOLOGY (Figs 14 & 15) For the most part the morphology of N. whoii is similar to that of N.salicensis. Of the mantle structures, the construction of the siphon is similar, although the siphonal embayment is less deep than in N. salincensis. The posterior adductor muscle is oval in cross-section and not much smaller than the anterior, probably reflecting the more rounded shell outline of N. whoii. The anterior sense organ is poorly developed, the least developed of all the deep-sea nuculanids that have been described to date. The gills and palps of N. whoii are similar in size and form to those in WN. salicensis with up to a maximum of 18 gill plates and 17 palp ridges. The foot is large with a few moderately deep papillae at the margin. The mouth lies some distance posterior to the anterior adductor. The stomach is large with 9 or 10 ridges forming the porterior sorting area. The hind gut makes a single loop to the right side of the body, the loop being somewhat larger and more smoothly curved than that in N. salicensis. The ganglia and commissures are not so stout as they are in the latter species. Clearly Neilonella whoii is closely related to N. salicensis. Although similar in form, they have markedly different depth distributions, N. salicensis occurring mainly at lower slope depths and N. whoii occurring mainly at abyssal depths. We believe that in the past there may have been misidentifications, and speci- mens of N. salicensis recorded from abyssal depths deserve re-examination. Specimens which are narrower and relatively smaller in height to length ratio than those described above (Fig.16) are present in some samples and do not occur other than with typical specimens of N. whoii. In other respects they are no different in their morphology to N. whoii. We consider them to be varients at the limit of a range of shell outlines and not a subspecies. DEEP-SEA PROTOBRANCHIA (BIVALVIA) taal | a un \ \ 2%, Y | Mi, it \\ aa f \ . / I \ YA , | I" : Fig. 12. Neilonella whoii. Details of shell form of specimens, from Chain station 78 from the North America Basin, the type locality; a, left lateral, b, dorsal and c, anterior views intact shells; d, the hinge plate of a specimen, from Incal station DSO5 from the West European Basin; e, detail of the umbonal region of the hinge plate of a specimen, from Chain station 78. Scales = 1mm. Fig. 13. Neilonella whoii. Four shells in outline, from Atlantis II station Fig. 14. Neilonella whoii. A semidiagrammatic view of the internal 72 from the North America Basin, in left lateral view to illustrate the morphology as seen from the right side. For the identification of the small changes in shape with increasing size. Scale = 1mm. parts see text-figure 7, p. 106. Scale = 1mm. 112 Fig. 15. Neilonella whoii. The dissected stomach and style sac as seen from a, in left lateral and b, frontal view. See abbreviations to text figures on p. 102. Scale = 1mm. Fig. 16. Neilonella whoii. a, right lateral view of shell of elongate form, from Atlantis II station 242 from the Argentine Basin, in right lateral view and b, detail of the umbonal region of the same shell in dorsal view. Scales = 1 mm. J.A. ALLEN AND H.L. SANDERS Family Nuculanidae Adams and Adams 1858 A recent definition of the family is given by Allen, Sanders and Hannah (1995). Subfamily Ledellinae Allen and Sanders 1982 The subfamily is defined by Allen and Hannah (1989) and comprises two genera, Ledella and Tindariopsis. Genus LEDELLA Verrill and Bush 1897 TYPE SPECIES. Ledella bushae Warén 1978. SD — Warén 1981. Shell small, short, robust, surface matt, concentric sculpture, in some species scattered incomplete radial striae, usually rostrate, single postero-dorsal ridge in some species, postero-ventral margin very slightly sinuous, ventral margin in older specimens maybe flattened, anterior and posterior hinge teeth series separated by edentulous space bearing short internal amphidetic ligament (resilium) which may be restricted to dorsal portion of hinge plate, outer layer of ligament visible externally and maybe extended anteriorly and posteriorly for a short distance, hind gut with various configurations. Genus TINDARIOPSIS Verrill and Bush 1897 TYPE SPECIES. Malletia (Tindaria) agatheda Dall 1889. OD. Shell veneriform, matt surface, concentric sculpture, umbo large, short rostrum defined by slight radial ridge and furrow, postero- ventral margin slightly sinuous, anterior and posterior hinge teeth separated by very small edentulous space, internal ligament small, close to shell margin, external ligament robust, amphidetic. Ledella acinula (Dall 1890) TYPE SPECIMEN. Holotype USNM 95438. TYPE LOCALITY. U.S. Fish Commission Steamer ‘Albatross’ Sta. 2754, 11.40'N 58°33'W, East of Tobago, 1609m. CITED SPECIMENS. BMNH 1995047 Malletia (Tindaria) acinula Dall, 1890, 253, pl. XIII, fig.4. Tindaria acinula Verrill and Bush 1898, 881. ‘Tindaria’ acinula Sanders and Allen 1977, 55, figs 44, 45. MATERIAL: Cruise Sta Depth No Lat Long Date Gear (m) BRAZIL BASIN AtlantisII 167 943- 1 07°58.0'S 3428.0'W 20.2.67 ES 31 1007 GUYANA BASIN Knorr 25 293 + 1456— 2 08°58.0'N 5404.3'W 27.2.72 ES 1518 295 1000— 4 O801.9'N 54°16.4';W 28.2.72 ES 1022 299 1942— 108 O755.1'N 5542.0'W 29.2.72 ES 2076 WEST EUROPEAN BASIN 50°43.5'N 17°51.7W 24.8.72 ES 4630.4'N 10°27.1'W_ 26.10.74 DS Chain 106 330 4632 3 J.Charcot DS79 3226 15 Biogas VI GUINEA BASIN J. Charcot DS28 1261 4 04°21.2'N 0435.E --71 DS Walda DEEP-SEA PROTOBRANCHIA (BIVALVIA) The type specimen has been examined by us. DISTRIBUTION. Found predominantly in tropical and subtropical latitudes, and southern temperate latitudes in the eastern Atlantic, at mid-slope to abyssal depths ranging from 943m to 4632m. Many protobranch species with robust shells having subrostrate or ovate outlines and with concentric ridges and external liga- ments, in the past have been referred to the genera Malletia, Neilonella orTindaria (e.g. Dall, 1890). Ledella acinula is a case in point. Having addressed this problem in earlier papers (Sand- ers and Allen, 1977, 1985), and the present, we have been able to define more rigorously the families Tindariidae, Neilonellidae and Malletiidae. Dall (1890) who described large specimens of L. acinula referred them to the subgenus Tindaria. Large specimens do show some resemblance to neilonellids and tindariids, but had Dall seen the shells of smaller specimens (Fig. 18), he would have been unlikely to have made the error. In our studies on Tindaria (Sanders and Allen, 1977) we re- examined and briefly redescribed L. acinula, and recognized that there was a problem in identification but deferred final judgment until we had made further comparative studies. Now that the Ledellinae have been reported upon (Allen and Hannah, 1989), the taxonomic relationship of this species is clear. That L. acinula is siphonate clearly distinguishes it from members of the family Tindariidae. Although similar to the neilonellids in having an external amphidetic ligament, it differs in having a small but well-defined internal ligament and in being semi-rostrate with a slightly sinuous postero-ventral margin. A further significant differ- ence is the form of the hind gut and the course that it takes within the body (Sanders and Allen, 1977). In L. acinula the hind gut is not particularly wide in diameter and is not restricted to the right side of the body (see below) having a configuration only known to occur in species of the subfamily Ledellinae e.g.Ledella galatheae Knudsen 113 1970, L. oxira (Dall 1927), L. acuminata (Jeffreys 1870)(Allen and Hannah, 1989). SHELL DESCRIPTION (Figs 17 & 18) Shell robust, posteriorly angulate, ornamented with concentric ridges particularly well-defined on ventral part of shell, straw-coloured periostracum; umbos relatively low in profile, inward facing, anterior to midline; posterior rostral region characteristically broad and blunt when seen in dorsal view; postero-dorsal shell margin almost straight, angulate at posterior limit of hinge plate - particularly so in smaller specimens, barely so in larger, posterior margin sharply rounded, ventral margin deeply curved, postero-ventral margin slightly sinu- ous, particularly in smaller specimens, antero-dorsal, anterior and antero-ventral margins form a smooth curve; posterior and anterior limits of shell at or slightly ventral to mid horizontal axis, ventral limit of shell posterior to vertical axis through umbo; hinge plate elongate, broad, anterior and posterior tooth series separated by relatively long edentulous space, chevron-shaped teeth acutely angled, up to 10 anterior and 12 posterior teeth depending on size of specimen; ligament amphidetic, external parts short, internal resilium small, rounded, occupying upper central part of hinge plate below umbo.The maximum total length of the present specimens is 6.0mm. The shape of the shell changes significantly with growth (Figs 18 & 19). While the ratio of height to length remains more or less the same, the postero-umbonal length increases from 50% to 60% of the total length of the shell. With increasing size the postero-dorsal margin also becomes less angulate at the posterior limit of the hinge, also the postero-ventral margin becomes less sinuous, at most being somewhat flattened. INTERNAL MORPHOLOGY This has been described and illustrated by us in our earlier studies on the family Tindariidae (Sanders and Allen, 1977). Only essential features relating to the taxonomy need be mentioned. Combined siphons are present and there is a well-developed Fig. 17. Ledella acinula. a & b, internal and external views of a left valve, from the type locality Albatross station 2754, USNM 95438; c, internal view of left valve of specimen, from Atlantis II station 167 from the Brazil Basin; d & e, lateral view of left side and dorsal view of a shell, from Knorr station 299 from the Guyana Basin. Scale = 1mm. 114 J.A. ALLEN AND H.L. SANDERS Fig. 18. Ledella acinula. Four shells in outline, from Knorr station 299 from the Guyana Basin, in right lateral view to illustrate changes in shape with increasing size. Scale = 1mm. feeding aperture ventral to the siphonal embayment. The adductor muscles are relatively large, the anterior ovate and the posterior more circular in cross section. The anterior sense organ lies far anterior, ventral to the anterior adductor. The palps and gills are moderate in size with relatively few ridges (up to 15) and plates (up to 17) respectively. The foot has a well-defined neck, this is probably related to the relatively large height of the shell. There is a large ‘byssal’ gland present in the heel of the foot. The hind gut first makes a single loop on the right side of the body before passing to the left side of the body between the oesophagus and the inner face of the anterior adductor muscle. On the left side of the body the hind gut forms a double coil. Because of the anterior penetration of the gut to the left side, the mouth is displaced some distance posterior to the anterior adductor muscle. 80 ie 2 @ H ee eg h © aa ro) F 70 60 : — = e oe, ~ © PL, one? L ae e 50 e 1 2 3 4 5 Length (mm) Fig. 19. Ledella acinula. The ratios of height to total length (H/L)(open circles) and post-umbonal length to total length (PL/L)(closed circles) plotted against total length to show changes in shell proportions with increasing length. Specimens from Knorr station 299 from the Guyana Basin. Ledella aberrata (new species) TYPE SPECIMEN. 1995046. Holotype BMNH 1995045; paratypes BMNH TYPE LOCALITY. Chain cruise 60, station 247, Argentine Basin, 43°33.0'S 48°58.1'W, 5208-5223m MATERIAL: Cruise Sta. Depth No Lat Long Date Gear (m) ARGENTINE BASIN Atlantis] 242 4382-2 3816.9'S 51°56.1;W 13.3.71 ES 60 4402 247 5208- 34 43°33.0'S 48°58.1'W_17.3.71 ES 5223 252 4435 4 38729.8'S 5209.1'W 223.71 ES GUYANA BASIN J.Charcot KG135100 1 1047.6N 42°40.4';W 20.11.77 KG Biovema NORTH AMERICA BASIN Chain 50 85 =. 338341 3759.2'N 69°26.2'W 5.7.65 ES WEST EUROPEAN BASIN Chain 106 330 4632 3 5043.4'N 17°51.7W 24.8.72 ES J.Charcot DS23 4734 5 4632.8N 1021.0';W 1.11.72 DS Polygas Biogas II DS32 2138 1 4732.2'N 0805.3'W 17.4.73 DS BiogasITV DS54 4659 7 4631.1'N 1029.2;W 21.2.74 DS Cryos DS68 4550 2 4626.7'N 1023.9'W 19.6.74 DS Biogas V J.Charcot DS78 4706 18 4631.2'N 1023.8'W 25.10.74 DS Biogas VI DS79 4715 17 4630.4'N 1027.1'W 26.10.74 DS DS80 4720 3 4629.5'N 1029.5'W 27.10.74 DS DS81 4715 2 4628.3'N 1024.6'W 27.10.74 DS INCAL CP10 4823 1 4825.5 N 1510:7W 3157-716 YEP DS11 4823 2 4818.8'N 15°11.5'W 1.8.76 DS WS034829 18 4819.2'N 1523.3'W_ 1.8.76 WS CP11 4823 1 48°20.4.N = 15'14.6'W_ 1.8.76 CP OS02 4829 1 48°19.2.N 15°15.9'W_ 2.8.76 OS WS104354 1 4727.3'N 09°39.9'W 11.8.76 WS CAPE BASIN J.Charcot DS05 4560 2 3320.5'S 0234.9'E 30.12.78 DS Walvis DEEP-SEA PROTOBRANCHIA (BIVALVIA) 115 Fig. 20. Ledella aberrata. a, dorsal view of shell; b, dorsal, ventral and anterior view of thickened shell; ¢, lateral view of the hinge plate of a left valve, all from Atlantis II station 247 from the Argentine Basin; d, lateral view of the hinge plate of a right valve, from Chain station 85. Scales = 1mm. DISTRIBUTION. In temperate and tropical basins of the Atlantic at abyssal depths >4000m, rare in the North America Basin. Depth range, 2138-5223m. SHELL DESCRIPTION (Figs 20 & 21) Shell small, ovate, relatively high, moderately wide, ornamented with concentric ridges; umbo moderate in size, inwardly turned, anterior to mid-line but less so in juveniles; no lunule or escutcheon; periostracum pale straw colour; postero-dorsal margin slightly con- vex becoming more straight with increasing size, slightly angulate at posterior limit of hinge plate and at posterior margin, postero-ventral margin very slightly sinuous, otherwise ventral margin deeply curved with ventral limit posterior to vertical axis through umbo, anterior margin sharply curved, antero-dorsal margin slightly convex with slight change in slope at anterior limit to hinge plate; shell outline characteristically asymmetrical, shell margin in larger specimens changes direction of growth producing a broad flattened ventral margin; hinge plate broad, up to 6 chevron teeth in anterior series and 7 in posterior series, edentulous space between series relatively broad; ligament small, amphidetic, internal part restricted to upper part of hinge plate, external part extremely short situated below umbo. The maximum length of the present specimens is 2.6mm. INTERNAL MORPHOLOGY (Figs 22 & 23) The adductor muscles are moderately large and oval in shape. The combined siphon is relatively short The dorsal margins of the exhalent part are fused proximally for a short distance and the ventral margins of the inhalent part are not fused but are slightly thickened and probably adhere in living specimens. Internally where inhalent and exhalent parts join, there is a thickened median ridge on each side which together together with the posterior continuation of the gill axes probably act as guides when the faecal pellets are extruded. The siphonal embayment is small and there is a small, slender, tentacle attached to the left side at the inner limit of the embayment. The anterior sense organ is small and is situated ventral to the anterior adductor muscle. The palps are small with up to 11 broad ridges. The gills are also small each with up to 11 plates the most posterior of which lies some distance from the siphon. The gills are attached to the posterior limits of the median guides by slender extensions of the gill axis. The hind gut is greatly extended and takes a similar but more complex course to that described for L. acinula. Like the latter, the hind gut passes from the right side of the body to the left immedi- ately posterior to the anterior adductor muscle and returns by the 116 Fig. 21. Ledella aberrata. Five shells in outline to show variation in shape with growth. a, is a specimen with a thickened margin; b, has a slightly thickened margin; the remaining three shells are unthickened. Scale = Imm. same route. Unlike the latter species, it makes a single coil on the right side as well as a double twinned coil on the left. The foot is unusual in having a large heel and a narrow muscular anterior part. The marginal papillae are few in number and restricted to the anterior margins of the sole. The sole is less deeply divided as compared with other protobranchs. There is a large “byssal’ gland in the heel of the foot. Although the shell outline of the smaller specimens is more characteristic of the genus Ledella than in larger mature specimens, the general shell outline of L aberrata (and L. acinula) is much deeper and more ovate than in other described species (Figs 18 & 21) nor is it markedly rostrate. Despite this, the characters place them in the Ledellinae (Allen and Hannah, 1989) and we see no reason for erecting another genus. Apart from L. aberrata, only two species of protobranchs, have been reported as exhibiting a change in shell growth to produce a flattened shell margin (Fig. 20). Both are ledellids, namely L. ultima (Smith 1885) and L. solidula (Smith 1885) (Allen and Hannah, 1989). Like L. aberrata these two latter species also have elongate hind guts. The hind gut of L. solidula is very similar to that of L. aberrata in having double twinned coils to the left side of the body (Fig.22), although it does not have an additional single coil to the right as does the present species. The type of course taken by the hind gut in L. acinula is also found in other species of Ledella (e.g. L. oxira) (Allen and Hannah, 1989). We named this species after the familiar appelation to which it was referred during our original analysis of the samples. Tindariopsis agatheda (Dall 1889) TYPE SPECIMEN. USNM 95437, lectotype here designated. TYPELOCALITY. U.S.Fish Commission Sta. 2754, east of Tobago, 11°40'N 58°33W, 1609m. J.A. ALLEN AND H.L. SANDERS Fig. 22. Ledella aberrata. Internal morphology as seen in a, right lateral view, b, left lateral view and ec, left ventro-lateral view. For identification of the parts see text-figure 7, p. 106. Scales = Imm. CITED SPECIMEN. BMNH 1995062. Malletia (Tindaria) agatheda Dall 1890, 252, pl. xiii, fig. 10. Tindaria (Tindariopsis) agatheda Verrill and Bush 1897, 59. Saturnia (Tindariopsis) agatheda McAlester 1969, N235. Tindariopsis agatheda James 1972, 98, figs 60-62. Neilonella (Tindariopsis) agatheda Laghi 1986, 190, pl.8, figs 2-6. MATERIAL: Cruise Sta Depth No _ Lat Long Date Gear (m) BRAZIL BASIN Atlantis 11 167 943- 1 0758.0'S 34°28.0'W 20.2.67 ES 31 1007 GUYANA BASIN Knorr 25 293 1456- 14 08°53.1'N 5404.3'W 27.2.72 ES 1518 299 1942-8 07°55.1'N 55°42.0'W 29.2.72 ES 2067 301 2487-7 0812.4'N 55°50.2'W 1.3.72 ES 2500 The type specimen has been examined by us. DEEP-SEA PROTOBRANCHIA (BIVALVIA) MM oOo Fig. 23. Ledella aberrata. Siphonal region, as seen from the inside of the mantle cavity. See abbreviations to the text-figures p. 102. Scale = 0.1mm. This species occurs at upper to mid slope depths in the tropical western Atlantic in the Brazil, Guyana, Caribbean and Gulf of Mexico Basins (Dall, 1889; James 1972). Depth range; 943—2500m. The holotype for 7: agatheda was not designated by Dall (1890), nevertheless he did illustrate the left valve from Albatross Sta. 2754, 11°40'N 58°33'W (USNM 95437) which we have here nominated as 117 lectotype. We have redrawn the shell and added detail of the hinge plate (Figs 24 and 25). In addition, James (1972) reported that two valves of T: agatheda were included in USNM 63149 from Blake sta. 236, 2909m off Bequia, furthermore USNM 94326 from Blake stas 26 and 30 between Cuba and Yucatan, identified by Dall as Leda pusio, are examples of T: agatheda. SHELL DESCRIPTION (Figs 24 & 25) Shell small, sub-ovate, wide, sub-rostrate, ornamented with con- centric ridges, postero-lateral furrow ventral to sub-rostrum, ill-defined lunule outlined by obscure ridge, escutcheon similarly ill-defined and bounded by faint ridge; umbo prominant, poste- rior to mid-line, inwardly directed; antero-dorsal margin concave, with change in slope at anterior limit of hinge plate, slightly flattened anteriorly dorsal to the anterior limit of shell, antero- ventral and ventral margins smoothly curved, postero-ventral margin slightly sinuate, posterior margin acutely angled, postero- dorsal margin slightly concave, marked angle at posterior limit of hinge plate and thereafter almost straight to form sub-rostrate posterior margin; anterior and posterior limits of shell are ventral to horizontal mid-line; hinge plate strong, with edentulous space ventral to umbo, hinge teeth stout, chevron-shaped, up to 12 in each series in shell 6mm total length; internal ligament small, close to shell margin, external ligament amphidetic, moderately short, stout. Young shells are less rostrate, with the posterior and anterior limits of the shell more dorsal in position. Although there is variation in the shape of the shell, the height/ length and the post-umbonal length/total length ratios increase slightly with increasing size (Table 1). The maximum total length of the present specimens is 6.0mm. Fig. 24. Tindariopsis agatheda. External lateral view of the right valve of the lectotype and an internal view of the hinge plate of the same valve, from U.S.Fish Commission station 2754 East of Tobago, USNM 95437. Scales = 1mm. 118 J.A. ALLEN AND H.L. SANDERS Fig. 25. Tindariopsis agatheda. External lateral views of right side of two specimens of differing size to show change in shape with growth. a, from Knorr station 301 and b, from Knorr station 293, both from the Guyana Basin; c, external dorsal view of a shell also from station 293. Scale = 1mm. Table 1. Measurements and ratios of shell parameters of the sample from Knorr sta. 293. Length(L) Height (H) Post-umbonal (PL) PL/L W/L (mm) (mm) length (mm) 6.00 4.95 3.00 0.50 0.83 5.60 3.95 2.65 0.47 0.71 5.00 3.65 2.20 0.44 = 0.73 4.90 3.65 2.05 042" 075 4.70 ByII5) 1.95 0.42 0.67 4.50 3.10 1.85 0.41 0.69 4.45 3.20 1.85 042) 1072 3.70 2.55 1.70 0.46 0.69 3.45 2.50 1.45 0.42 0.73 2.35 1.58 0.93 OSS OlGy 2.05 1.43 0.93 0.45 0.70 1.95 1.30 0.88 0.45 0.67 1.83 1.28 0.83 0.45 0.70 1.10 0.88 0.48 0.43 0.80 INTERNAL MORPHOLOGY (Fig.26) The siphonal embayment is shallow and dorso-ventrally narrow. In contrast, the feeding aperture is broad and well-supplied with radial pallial muscles. The adductor muscles are small, the posterior muscle is oval and the anterior muscle is circular in cross section. The foot is large with a well-developed heel containing a large ‘byssal’ gland. The gland opens into the posterior limit of the pedal groove via a small papilla. The anterior two-thirds of the margins of the divided sole are broadly papillate. The palps are large with up to 25 ridges in the largest specimens. The gills are narrow ill-defined with about 16 plates in the largest specimens. The mouth lies close to the posterior face of the anterior adduc- tor muscle. The oesophagus opens into a large stomach and style sac. The hind gut passes posterior to the style sac and stomach to the dorsal side of the viscera and thence across the right side of the body where it forms 8 coils before returning along the same path to the dorsal side of the viscera and from there through the heart and then dorsal to the posterior adductor muscle to the anus. Usually not more than six coils are visible, the others being overlain by those to the outside of them. The form of the hind gut is derived by 4 complete turns of the closely parallel anterior and posterior lengths of the hind gut on the right of the body. This particular disposition of the hind-gut is to be found in other ledellids (e.g. L. ultima) and yoldiellids (e.g. ¥. ella Allen, Sanders and Hannah 1995) (Allen and Hannah, 1989; Allen, 1992: Allen, Sanders and Hannah, 1995). The nervous system is similar in its arrangement to that of other deep-sea protobranchs, however the cerebral and visceral ganglia are noticably smaller and the commissures much finer than observed in other species. Fig. 26. Tindariopsis agatheda. Internal morphology as seen from the right side of a specimen from Knorr station 293. For identification of the parts see text-figure 7, p. 106. Scale = 1mm. DEEP-SEA PROTOBRANCHIA (BIVALVIA) Tindariopsis aeolata (Dall 1890) TYPE SPECIMEN. Holotype, USNM 95436. TYPELOCALITY. U.S. Fish Commission Sta. 2754, East of Tobago, 11°40'N 58°33'W, 1609m. CITED SPECIMEN. BMNH 1995061. Malletia (Tindaria?) aeolata Dall 1890, 252. Tindaria (Tindariopsis) aeolata Dall 1898, 582. Tindariopsis aeolata James 1972, 97, figs 57-59. MATERIAL: Cruise Sta. Depth No _ Lat Long Date Gear (m) GUYANA BASIN Knorr 25 299 1942-4 O755.I'N 55°42.0'W 29.2.72 ES 2076 301 2487-5 08°12.4'N 55°50.2'W_-.29.2.72 ES 2500 The type specimen has been examined by us. This species occurs from mid to lower slope depths in the tropical western Atlantic in the Guyana and Caribbean Basins and the Gulf of Mexico. Depth range: 1609-3466m. SHELL DESCRIPTION (Figs 27 & 28) Shell small, subquadrate, rostrate, ornamented with marked concen- tric ridges; periostracum pale yellow; umbos moderately large, posterior to midline (post-umbonal length 45-48% of total length), facing inwards, slightly separated by external ligament; distally antero-dorsal shell margin horizontal, then curves smoothly and steeply to anterior margin, postero-ventral margin sinuous, ventral margin somewhat flattened, postero-dorsal distal margin slopes gently to limit of hinge plate then curves sharply to rostral point, latter rounded and somewhat eroded in large specimens, more pointed in smaller, rostrum in mid horizontal plane in small speci- mens and dorsal to it in large specimens, limit of anterior margin Fig. 27. Tindariopsis aeolata. External lateral view of the right valve and the hinge plate of the left valve of the holotype, from U.S. Fish Commission station 2754, USNM 95436. Scale = 1mm. 119 C Fig. 28. Tindariopsis aeolata. External lateral views of the right side of shells of differing size to change in shape with growth. a, from Knorr station 301 and b, from Knorr station 299 from the Guyana Basin; c, external dorsal view of a shell also from Knorr station 299. Scales = |mm. ventral to the mid horizontal plane; hinge plate stout, small edentu- lous space between tooth series, 9 chevron-shaped teeth in anterior series and 10 in posterior series in largest specimens; ligament amphidetic, external except for small resilifer at margin ventral to umbo, external part thickened, particularly so in large specimens. The maximum length of the present specimens is 5.8mm. In lateral view the rostrum, although dorsal to mid horizontal line, is reminiscent of Ledella, while the robust external ligament is more reminiscent of Spinula. INTERNAL MORPHOLOGY (Fig.29) The siphonal embayment is relatively shallow and the contained siphon is similar to that of 7: acinula. The adductor muscles are moderately small, ovate in cross-section and equal in size. The foot is large, with a divided sole fringed with large papillae. The “byssal’ gland is moderate in size. The palps are very large with many ridges (c 26 in the largest specimen) and the palp proboscides are broad. The gills are small with 11 gill plates in the largest specimen. The kidney is long and narrow. The nervous system is of typical protobranch design. The ganglia are relatively large and, in contrast, the commissures are unusually slender. The mouth lies some distance posterior to the anterior adductor muscle (see below). The oesophagus opens on to the anterior face of a moderately large stomach. The latter lies almost vertical within the posterior part of the visceral mass. The hind gut is very small in diameter and takes an extraordinarily complex course through the body. There are two loops to the left side of the body (Fig.29B) and one major loop to the right side of the body, all three pass from one side to the other ventral to the umbo. There is also a complex series of loops anterior and to the right of the stomach. This morphology has not been encountered before in the protobranch bivalves and is very different from that seen in 7: agatheda. Yet, it is debateable 120 Fig. 29. Tindariopsis aeolata. a, internal morphology as seen from the right side of a specimen from Knorr station 301 from the Guyana Basin; b, the form of the hind gut on the left side of the body. For identification of the parts see text-figure 8, p.. Scale = 1mm. whether the difference warrents generic status. Other protobranch genera show an array of hind gut morphologies (e.g. Yoldiellidae, Allen, 1992; Allen, Sanders and Hannah, 1995) which we believe relate to changes in the benthic food resource as depth increases. For this reason we are reluctant to erect a new genus when in other respects 7: aeolata is clearly within the genus Tindariopsis. Subfamily Nuculaninae Allen and Sanders 1982 The subfamily is defined by Allen and Hannah (1986) and comprises three genera Nuculana, Propeleda and Adrana. Genus NUCULANA Link 1807 TYPE SPECIES. IWS, OIDY Shell robust, moderately elongate, concentric sculpture, occa- sionally with radial ribs, slightly rostrate, usually bicarinate; umbo anterior; postero-dorsal margin straight or somewhat concave, pos- terior margin may be slightly sinuous; escutcheon present; no internal ridge from umbo to posterior margin; hinge moderately robust, teeth chevron-shaped; ligament small, for most part internal, usually amphidetic and vertical, sometimes posteriorly oblique. Arca rostrata Gmelin 1791 = Arca pernula Miller Genus PROPELEDA Iredale 1924 TYPE SPECIES. Leda ensicula Angas 1877. OD. Shell very elongate, thin, glossy, concentric sculpture may be ill- defined, 3/4 shell post-umbonal, usually with two marked carinae from umbo to upper and lower limit of rostrum, posteriorly truncate; umbo small; postero-dorsal margin concave, postero-ventral margin not sinuous; internal ridge usually from umbo, skirts ventral margin of posterior adductor to posterior margin, second ridge may be present from hinge plate to rostral margin; hinge plate slender, hinge J.A. ALLEN AND H.L. SANDERS teeth chevron-shaped, one or both arms of the chevron may be elongate, anterior tooth series curve round the outer margin of the anterior adductor, posterior series extends posterior to adductor; ligament in large part internal, opisthodetic and oblique. Genus ADRANA Adams & Adams 1858 TYPE SPECIES. Nucula lanceolata Lamarck 1819. SD Stoliczka 1871. Shell extremely elongate, slender, lanceolate, fragile, smooth or with fine concentric and sometimes oblique sculpture, without carinae, glossy; umbo almost central, barely raised; escutcheon elongate, flattened, narrow; postero-dorsal margin straight, antero- dorsal margin slightly convex, postero-ventral margin sinuous; hinge plate slender, hinge teeth fine, obtuse, chevron-shaped; chondrophore present; ligament internal, amphidetic. Nuculana acuta (Conrad 1831) TYPE SPECIMEN. Lectotype here designated, chosen from ANSP 30613, remainder of lot designated paralectotypes. CITED SPECIMEN. BMNH 1995055. TYPE LOCALITY. Tertiary fossil beds, near Suffolk, Virginia. Nucula acuta Conrad 1831, 32, pl.6, fig.1. Nucula cuneata Sowerby 1833, 198. Nucula carinata H.C.Lea 1843, 163, (non M’Coy 1844). ?Leda jamaicensis ad’ Orbigny 1846, 263, pl.XXIV, figs 30-32. ?Leda inornata A.Adams 1856, 48. Leda unca Verrill 1880, 401, (?non Gould 1862). Leda acuta Dall 1886, 251, pl.7, figs 3a, 3b and 8. Nuculana acuta Morris 1951, 7, pl.6, fig.2. MATERIAL: Cruise Sta’ Depth No Lat Long Date Gear (m) NORTH AMERICA BASIN Atlantis Cl 97 24+2v 40°20.5'N 70°47.0'W 25.5.61 AD 264 Atlantis Slope 200 8+6v 4001.8'N 7042.0';W 28.8.62 AD 283 sta.2 AtlantisII 114 197 8 40°04.1'N 7027.8'W 15.8.66 ES 24 AtlantisII 172 119 7+2v 40°12.3'N 7044.7';W 27.11.67ES 40 Visi e23 4 40°10.8'N 70°43.6'W 28.11.67 ES The type specimens have been examined by JAA. Conrad (1831) described this species from fossils obtained from the Miocene beds near Suffolk and the banks of the James and York rivers, Virginia. He later redescribed the species (Conrad, 1845) adding that he had found Recent specimens in deep water in the Gulf of Mexico. His first account refers to specimens being in “Cabinet of the Acad. Nat. Sciences, No.1738. This reference does not corre- spond with any lot of NV. acuta, Recent or fossil, in the Academy of Natural Sciences, Philadelphia today. There are specimens in the Invertebrate Paleontology collection of the Academy (catalogue number 30613) that up to now have been considered as possible syntypes of the species. The lot comprises 4 right valves, 3 left valves | left and | right broken valve, | intact shell, 1 shell with rostrum tip missing and 3 fragments. These specimens, labelled by DEEP-SEA PROTOBRANCHIA (BIVALVIA) 121 Fig. 30. Nuculana acuta. a & b, lateral and dorsal external views of the lectotype, ANSP 30613; c, lateral internal view of a paralectotype from the same lot. Scales = 1mm. Conrad, may include those figured by him. Comparison with the figures (Conrad, 1831 and 1845) shows that it is impossible to say which, if any one, was figured nor is it possible to be absolutely certain that these are the specimens from which the original descrip- tion was made, although we believe that they are. Thus, the intact shell from lot 30613 has been chosen as the lectotype, the remainder being paralectotypes. Campbell (1993) listed Leda jamaicensis d’Orbigny 1846, Leda Fig. 31. © Nuculana acuta. Lateral and dorsal external views of a shell, from Atlantis 283 station 2 from the North America Basin. Scales = Imm. inornata A.Adams 1856 and L.unca Gould 1862 as synonyms of N. acuta. Verrill (1882) describes in detail differences that he found between N. acuta and L.jamaicensis and L.unca which cast doubt as to the synonymy, although Dall (1886) maintains the synonymy of L. jamaicensis. Similarly, we have doubts as to synonymy with L.inornata A.Adams which is a ‘gibbose’, “fuscous’, ‘sulcate’ spe- cies from New Guinea, Thus, although Nuculana acuta is a well-described species (e.g. Verrill 1882, 1884; Dall, 1886; Abbott, 1974) because there are closely related species in the Atlantic and elsewhere, we include a description here. It occurs off the East coast of North America, in the Caribbean Sea and off Brazil at depths from the outer shelf to lower slope depths, 97—2909m (James, 1972). SHELL DESCRIPTION (Figs 30, 31) Shell moderately large, elongate, somewhat inflated, rostrate, ornamented with deep concentric ridges flattened at the apex, rostral ridge from umbo to ventral limit of rostrum, very faint radial ridge from umbo to antero-ventral margin, yellow periostracum; lunule Fig. 32. Nuculana acuta. Internal morphology as seen from the right side of a specimen from Atlantis II station 197 from the North America Basin. For identification of the parts see text-figure 7, p. 106. Scale = 1mm. 122 SP (Zp) a Miinacs iN Ms \\ we IS > rS | J.A. ALLEN AND H.L. SANDERS Gl FG Moga Fig. 33. Nuculana acuta. Internal morphology, a, anterior, b, left lateral & c, posterior views of a dissected stomach and combined style sac; d, ventral view of siphonal region. See abbreviations to text-figures on p. 102. Scales = 1mm. broad, elongate, outlined with faint ridge, escutcheon broad, out- lined by rostral ridge; umbos small, inwardly directed, anterior to mid-line; antero-dorsal margin broadly concave, anterior, antero- ventral, ventral and postero-ventral margins form smooth curve, postero-dorsal margin raised, distally straight, proximally — poste- rior to hinge plate — slightly concave, may be slightly upturned in larger specimens; hinge plate elongate, relatively broad, hinge teeth chevron-shaped, up to 18 teeth in each series depending on size of specimen; ligament small, amphidetic, internal pear-shaped in sag- ittal section, extends slightly ventral to hinge plate. The maximum length of the present specimens is 9.2mm. INTERNAL MORPHOLOGY (Figs 32, 33) The siphonal embayment is deep, with an elongate tentacle attached to the inner right or left side. The siphons are elongate, combined and except anteriorly, the ventral margins are fused. In the con- tracted state the line of fusion is marked by deep ventral furrow. The anterior sense organ is far anterior, situated at the point where the radial ridge meets with the shell margin. Between the feeding (ventral to the siphonal embayment) and the pedal gape, the inner folds of the ventral margin are applied to each other. In this section of mantle margin approximately 30 small sensory papillae are attached to each middle sensory fold in a specimen 6.5mm total length. The adductor muscles are small the anterior unusually so. The anterior adductor is circular in cross-section and the posterior elongate-oval. The foot is moderately large, elongate, the sole with papillate margins. The heel is not marked but there is a a large “byssal’ gland present internal to the posterior limit of the sole. The gills are well- developed with up to 48 alternating gill plates. The dorsal margins of the left and right inner demibranchs are fused. In life the gills are a bright orange-red colour. In contrast the palps are cream. The latter are relatively small, elongate and dorso-ventrally narrow and, for the most part, hidden under a fold of the body wall. This latter is more pronounced on the right side of the body where the hind gut loop meets the ventral margin of the visceral wall. Each palp has up to 24 ridges on the inner face. The palp proboscides are also long and tapering. The digestive gland is bright orange in life. As in other species of Nuculana, the course of the hind gut describes a single loop to the DEEP-SEA PROTOBRANCHIA (BIVALVIA) right side of the viscera. There is a single typhlosole present along its entire length. The stomach is of moderate size and internally is similar in form to that of shallow water species of Nuculana (Yonge, 1939). The gastric shield lines much of the left wall of the stomach. To the right there is a large posterior sorting area with 13 ciliated ridges. A deep caecum is ventral to the oesophageal aperture. Two digestive ducts open close to the antero-dorsal margin of the poste- rior sorting area and a single duct opens antero-dorsally close to the oesophageal opening. As will be seen Nuculana acuta is remarkably similar in its shell features and anatomy to Nuculana commutata. This similarity is discussed under the latter species (p. 123). Nuculana commutata (Philippi 1844) TYPE SPECIMEN. ZMHU. TYPE LOCALITY. Pliocene, Palermo, Sicily. BMNH 1995212 Arca fragilis Chemnitz 1784, 199, pl.LV, fig.546. Arca pella Gmelin 1790 (non Linné), 3307. Arca minuta Brocchi 1814 (non Fabricius), 482, pl. XL fig.4. Nucula pella Payraudeau 1826 (non Linné), 64. Lembulus deltoideus Risso 1826 (non Lamarck), 320, pl. XI, fig. 164. Nucula minuta Scacchi 1836 (non Fabricius), 4. Nucula striata Philippi 1836 (non Lamarck), 64. Nucula commutata Philippi 1844, 101. Leda fragilis Jeffreys 1879, 575. Leda minuta Jeffreys 1856 (non Fabricius), 25. Leda commutata Hanley 1863, pl.CCXVIILI, figs, 80, 81. Lembulus commutatus Monterosato 1878, 6. Leda (Portlandia) tenuis Sturany 1896, 6. Nuculana (Jupiteria) fragilis Nordsieck 1969, 9, pl.1, fig.02.25. Nuculana (Jupiteria) commutata Smith and Heppell 1991, 56. CITED SPECIMEN. MATERIAL: Cruise Sta. Depth No Lat Long Date Gear (m) WEST EUROPEAN BASIN Sarsia 529 119 16 4740.0'N 05°00.0'W 12.8.67 ES SHELL DESCRIPTION (Fig.34) Shell moderately large, elongate, slightly inflated, rostrate, ornamented with concentric ridges, pale straw-coloured perio- stracum; radial ridge from umbo to antero-ventral margin; rostral ridge well-defined, delimits posterior dorsal area, within this area a faintly outlined escutcheon extending half the length of postero- dorsal margin; lunule elongate, defined by fine ridge; less well-defined ventral rostral ridge extends from umbo to postero- ventral margin; umbos anterior to midline, inwardly directed; antero-dorsal margin proximally straight, distally slightly concave merging with rounded anterior margin to where it meets with ventral limit of anterior radial ridge, ventral margin broadly concave, postero- ventral margin sinuate where ventral rostral ridge meets margin, posterior margin acute, slightly upturned, postero-dorsal margin slightly raised with shallow angulation at limit of hinge plate; hinge plate elongate, relatively broad, acute chevron teeth, 16 on both anterior and posterior hinge plates of specimen 8.3mm total length; ligament internal, amphidetic, triangular, extends slightly ventral to hinge plate. Fig. 34. Nuculana commutata. Lateral and dorsal views of a shell, from Sarsia station $29 from the West European Basin. Scale = 1mm. Maximum length of present specimens is 8.3mm. INTERNAL MORPHOLOGY (Fig.35) The internal morphology differs little from that of NV. acuta (Fig.32). The most noticable differences are that N. commutata has less attenuate palps with fewer palp ridges and larger adductor muscles than does N. acuta. Other differences between the two species are that in. commutata the ridge from the umbo to the antero-ventral margin is more marked, the apices of the concentric ridges are less broad, the postero-dorsal margin is not so raised and the shell is somewhat less elongate in relation to its height. These differences are of degree and at that point where separation into species rather than subspecies is a subjective judgement. Never- theless, these differences are more marked than those between N. commutata andN. illiricaCarrozza 1987 (paratypes BMNH 1995213 examined by JAA), a species that has been recently described from the northern Adriatic Sea (Carrozza, 1987). In contrastN. commutata Fig. 35. © Nuculana commutata. Internal morphology as seen from the right side of a specimen from Sarsia station $29 from the West European Basin. For identification of the parts see text-figure 7, p. 106. Scale = 1mm. 124 is widely distributed throughout the Mediterranean and lusitanean Atlantic. Prior to the paper by Carrozza (1987) there had been debate as to whether N. fragilis and N. commutata were the same species (Locard, 1891, 1898; Bucquoy et al, 1887-98). It is not possible to determine whether this earlier debate was a presage to the study of Carrozza (1987). In contrast NV. acuta is even more widely distrib- uted off the eastern North America, West Indies and off Brazil (Abbott, 1974). It must be assumed that these are three sibling species. Nuculana vestita (Locard 1898) MNHN TYPE LOCALITY. Talisman stas 96-98 & 101, West of Senegal, 2324-3200m, 19°12'N 17°57'W — 1638'N 18°24'W CITED SPECIMENS. BMNH 1995056 and 1995211 Leda vestita Locard 1898, 340, pl.XIV, figs 12-18 Nuculana vestita Clarke 1962, 53. Leda macella Barnard 1963, 448, fig.11d; type locality: West off Cape Point, S.W.Africa, Africana II stas A190, A192, A317, A319, 2268—-3200m, SAM (not seen). TYPE SPECIMEN. MATERIAL: Cruise Sta Depth No Lat Long Date Gear (m) SIERRA LEONE BASIN Atlantis II 146 2842 1 10°39.5'N 1744.5';W 6.2.67 ES 31 —2891 ANGOLA BASIN AtlantisI] 201 1964 1 09°29.0'S S40. y 2356s ES 42 —2031 203 527 £742 0846.0'S 1247.0'E 23.5.68 ES —542 J.A. ALLEN AND H.L. SANDERS Specimens taken by the Galathea Expedition described by Knudsen (1970) examined by JAA, ZMUC. Knudsen (1970) fol- lowing examination of specimens synonymized L. macella with N. vestita. Nuculana vestitais a well-described species (Locard, 1898;Theile and Jaeckel, 1931; Knudsen, 1970) occurring off West and South- west Africa at lower slope depths (715—2891m) in the Sierra Leone, Guinea and Angola basins. SHELL DESCRIPTION (Figs 36 & 37) Shell moderately large, inflated, somewhat elongate, rostrate, ornamented with concentric ridges, pale brownish-yellow periostracum; umbos large, inwardly directed, anterior to midline; antero-dorsal distal margin horizontal for short distance, proximal margin broadly convex forming smooth curve with anterior margin, ventral margin broadly convex to rostrum, postero-dorsal margin, raised in small specimens but less so in large, proximally straight or slightly concave, in small specimens angulate at limit of posterior hinge plate, distally slightly concave to posterior limit of rostrum; broad ridge extends from umbo to rostrum forming outer limit of escutcheon; anterior and posterior hinge plates broad, meet shell margin ventral to umbo, hinge teeth broad chevrons, up to 19 and 16 in anterior and posterior series respectively in specimen 8.3mm total length; ligament internal, amphidetic, pear-shaped in sagittal verti- cal section, extends ventral to hinge plate. The maximum length of the present specimens is 13.8mm. INTERNAL MORPHOLOGY (Fig. 38) The adductor muscles are moderately large and oval. The siphonal embayment is deep with the siphonal tentacle to the right side. The siphons are entire. The feeding aperture is small but well-defined with the mantle surface ridged internally. Radial mantle muscles are well-developed forming a broad band internal to the inner lobe Fig. 36. Nuculana vestita. External right lateral and dorsal view of a large adult shell and a lateral view of the hinge plate of a right valve. Specimens are from Atlantis II station 203 from the Angola Basin. Scale = 1mm. DEEP-SEA PROTOBRANCHIA (BIVALVIA) 125 Fig. 37. Nuculana vestita. Lateral views of right side of four shells in outline to show differences in shape with increasing size. Specimens from Atlantis II station 203 from the Angola Basin. Scale = 1mm. of the mantle edge. The anterior mantle sense organ is well- developed. The foot is large with the margins of the sole finely papillate. The palps are very small with up to 12 broad folds. The palp proboscides are stout and elongate, even in the contracted state. The gills are elongate and broad with up to 36 gill plates. Propeleda carpenteri (Dall 1881) TYPE SPECIMEN. Syntypes, USNM 63151 and MCZ 7936-7938. TYPE LOCALITY. Off Barbados, ‘Blake’ stations 5, 9, and 21, 100fm—287fm. BMNH 1995057 Leda carpenteri Dall 1881, 125; 1886, 249, pl.8, fig.10, pl.9, fig.3. Nuculana carpenteri Johnson 1934, 16. CITED SPECIMENS. MATERIAL: Cruise Sta. Depth No Lat Long Date Gear (m) ARGENTINE BASIN AtlantisII 237 993- 194 3632.6'S 5323.0';W 11.3.71 ES 60 1011 239 1661-8 3649.0'S 53°15.4;W 11.3.71 ES 1679 240 2195-8 3653.4'S 53°10.2';W 12.3.71 ES 2323 Specimen USNM 63151 examined by JAA. Previously reported off N. Carolina, Gulf of Mexico and Eastern Caribbean (Dall, 1889; Rice and Kornicker, 1965; James, 1970), the present specimens are from the Argentine Basin. This species has a Fig. 38. Nuculana vestita. Internal morphology as seen from the right side of a specimen from Atlantis II station 203 from the Angola Basin. For identification of the parts see text-figure 7, p. 106. Scale = 1mm. somewhat unusual distribution from shelf to lower slope depths, 200-2323m SHELL DESCRIPTION (Figs 39-41) Shell fragile, semi-transparent, slender, moderately elongate, rostrate with two post umbonal carinae, ornamented with faint concentric ridges; periostracum pale straw colour; umbos small, far anterior (postumbonal length 60-68% of total length), inwardly facing; antero-dorsal margin slightly flattened, ventral margin smoothly curved, postero-dorsal margin raised, slightly sinuous, concave proximally, convex distally, meets posterior margin at limit of dorsal post-umbonal carina, posterior margin concave between posterior 126 J.A. ALLEN AND H.L. SANDERS -—_— Fig. 39. Propeleda carpenteri. External lateral view of the left valve and an internal view of the same valve of a syntype USNM 63151, from off Barbados in 100fms. Scale = 1mm. limits of dorsal and ventral carinae; escutcheon lanceolate; hinge plates relatively broad, posterior plate short, occupying little more than half of postero-dorsal margin, anterior plate approximately half length of posterior, hinge teeth acute chevron-shape, relatively few in number, up to 18 in posterior series and 16 in anterior; ligament internal, oblique, posterior to umbo; internal shell ridge extends from mid posterior margin to approximately opposite the mid-point of the posterior hinge plate between and parallel to the lines of the post-umbonal carinae.The maximum length of the present speci- mens is 15.3mm. In most specimens the posterior shell margin is damaged, often being markedly shortened and specimens frequently show regenera- tion of the shell posterior to the posterior adductor. The repaired shell is without concentric ornamentation. It is possible that ex- tended siphons are predated upon and that the shell is damaged when this occurs. ——_ ee \ Fig. 40. Propeleda carpenteri. External lateral view of the right side of a shell and an internal lateral view of a right valve from Atlantis II station 237 from the Argentine Basin. Scale = 1mm. DEEP-SEA PROTOBRANCHIA (BIVALVIA) Fig. 41. Propeleda carpenteri. External lateral views of the right sides of two small shells to show differences in shape from the specimen illustrated in text-figure 40. Specimens taken from Atlantis II station 239 from the Argentine Basin. Scale = 1mm. The concentric ridges on the shell of the present specimens while not particularly marked are more so than those described by Dall, though the syntypes that we have examined are dead valves that are somewhat worn (Fig.39). Our specimens also are very slightly more anteriorly extended than the syntypes, though the characteristic antero-dorsal curvature of the shell margin is the same. Our speci- mens correspond well with the figures given by James (1972, figs 67 and 68). These latter come are from similar depths (2340—2627m) to some of our own. It would appear that specimens from mid to lower slope differ slightly from those taken at shallower depths however, we regard the differences as being at most infrasubspecific. There is a marked change in shape during growth. Juveniles are much shorter than the adults and subsequent growth involves in- creasing elongation of the post-umbonal shell. The prodissoconch is extremely large measuring 630um in length. 127 INTERNAL MORPHOLOGY (Fig.42) The adductor muscles are oval in cross-section, the posterior being the more fusiform, both are set some distance in from the shell margin. The posterior adductor muscle lies opposite the limit of the posterior hinge plate, the anterior muscle is attached to the shell just dorsal of the mid-horizontal shell axis. The siphonal embayment is elongate, the siphons are slender and entire. The anterior sense organ is small in size. The foot lies in the anterior half of the mantle cavity in preserved specimens, it is relatively elongate and has numerous small papillae present along the margins of the sole. The palps are small, each bearing an extremely long, narrow, palp proboscis. Depending on the size of the specimen there are up to 17 palp ridges. The gills are elongate, slender, and have up to 17 plates. The course of the hind gut is similar to that in Nuculana in that it passes to the right side of the body where it forms a broad loop that passes close to the posterior wall of the anterior adductor muscle. The stomach is large and occupies a vertical position in the posterior part of the visceral mass. The digestive gland is extensive occupying much of the antero-dorsal visceral space. Propeleda louiseae (Clarke 1961) TYPE SPECIMEN. Holotype, MCZ 224958. TYPE LOCALITY. R.V.Vema biology station 121, Argentine Basin, 1000 miles ESE of Buenos Aries, 5105 metres. CITED SPECIMENS. BMNH 1995058 Nuculana (Thestyleda) louiseae Clarke 1961, 375, pl.1, fig. 7. MATERIAL: Cruise Sta Depth No Lat Long Date Gear (m) ARGENTINE BASIN Atlantis II 242 4382— 25 3816.9'S 5156.1°W 13.3.71 ES 60 4402 243 3815— 2 3736.8'S 5223.6'W 14.3.71 ES 3822 247 = 5208- 2 43°33.0'S 48°58.1'W_17.3.71 ES 5223 256 3906- 3 3740.9'S 52°19.3'W 24.3.71 ES 3917 Fig. 42. Propeleda carpenteri. Internal morphology as seen from the right side of a specimen taken from Atlantis II station 239 from the Argentine Basin. For identification of the parts see text-figure 7, p. 106. Scale = 0.5mm. 128 J.A. ALLEN AND H.L. SANDERS Sse Fig. 43. Propeleda louiseae. a & b, external lateral views of the right sides of shells of differing size to show differences in shell proportions with growth; note outline internal morphology through semi-transparent shells, in particular the form of the hind gut and position of the adductor muscles; c, outline of shell from the left side showing the outline of hind gut and adductor muscles; d, internal view of a left valve. All specimens taken from Atlantis II station 242 from the Argentine Basin. Scales = 1mm. Type specimen examined by HLS. Distributed at abyssal depths in the Argentine Basin; depth range: 3815-5223 metres. SHELL DESCRIPTION (Fig.43) Shell extremely elongate, slender, fragile, semi-transparent, ornamented with moderately spaced concentric ridges, two post- umbonal rounded ridges, one dorsal and one ventral at posterior shell margin and crossed vertically by wavy continuations of the concentric ridges, faint anterior radial ridge from umbo to antero- ventral margin; umbo slightly raised, far anterior (post-umbonal length 65-70% of total length), inwardly facing; antero-dorsal margin with short proximal notch, distally margin raised and slightly concave, faint angulation before anterior margin, anterior margin joins with ventral margin in smooth curve, postero-ventral margin very slightly sinuate, posterior margin angled and sinuate, postero- dorsal margin notched at umbo, distally somewhat raised and keeled, concave overall but slightly sinuous dorsal to hinge plate; hinge plate relatively broad, posterior plate short occupying approxi- mately half the postero-dorsal shell margin, hinge teeth elongate, acute chevron shape, up to 12 in anterior and 20 in posterior series; ligament small, internal, oblique, pear-shaped; rounded internal ridge extends from umbo to posterior margin and marks junction between inhalent and exhalent siphons. The maximum length of the present specimens is 20.3mm. The prodissoconch is large measuring 300um in length. Clarke (1961) records a long, thin, external ligament in the type specimen — the latter being a single large valve. We find no evidence of an external part to the ligament and believe that Clarke mistakenly confused periostracum along the postero-dorsal margin for liga- ment. INTERNAL MORPHOLOGY With one notable exception the internal morphology of Plouiseae differs little from that of P carpenteri. Unlike the latter species the hind gut of P. louiseae first passes to the left side of the body where it forms a relatively small loop immediately ventral to the umbo (Fig.43). From there it passes to the right of the body and forms a loop that is considerably larger than that on the left although not as extensive as that in P. carperteri (Figs 42 & 43). The adductor muscles are relatively large, the elongate poste- rior muscle is situated at the distal limit of the posterior hinge plate. The gill is very short and slender with few (c. 13) gill- plates. Propeleda paucistriata (new species) TYPE SPECIMEN. 1995060. Holotype BMNH 1995059; Paratypes BMNH TYPELOCALITY. Atlantis II station 203, Angola Basin, 08°48.00'S 12'52.00'E, 527-542m. DEEP-SEA PROTOBRANCHIA (BIVALVIA) MATERIAL: Cruise Sta Depth No Lat Long Date Gear (m) ANGOLA BASIN AtlantisII 203 527— 31 0848.00'S 12°52.00E 23.5.68 ES 42 542 DISTRIBUTION. Restricted to the Angola Basin at upper slope depths, 527-542 metres. SHELL DESCRIPTION (Fig.44) Elongate, fragile, transluscent shell, moderately slender, two cari- nate ribs from umbo to posterior margin, widely spaced prominant, relatively broad, concentric ribs with overhanging ventral margin, 24 fine concentric lines between ribs, between carinae vertical ribs and lines equally prominant; umbo moderately raised, far anterior in largest specimens (post-umbonal length 79% of total length) but less so in smaller specimens, beaks inwardly facing; antero-dorsal mar- gin sloping, proximally convex but almost straight in small specimens, joins with anterior and antero-ventral margins in smooth curve; postero-ventral margin very slightly sinuous, posterior margin usu- ally damaged in large specimens, intact margin angled and sinuate, forming a hook dorsally where postero-dorsal margin and dorsal carina meet, postero-dorsal margin concave, proximally raised, elongate escutcheon outlined by dorsal carina; hinge elongate, moderately broad, large, acute chevron-shaped teeth up to 16 in anterior series and up to 28 in posterior series, anterior series extends to anterior limit of anterior adductor muscle, posterior series extends approximately half length of postero-dorsal margin to anterior limit 129 of posterior adductor muscle, ventral margin of hinge plate corre- sponds to line of dorsal carina, ventral to umbo teeth approach shell margin, anterior and posterior hinge plates continuous; ligament internal, ventral to umbo and close to shell margin, slightly inclined posteriorly; rounded internal ridge extends from umbo to posterior margin. The maximum recorded shell length is 14.1mm. The prodissoconch is very large and measuring 560um in length. Juvenile shells are more ovate and, before posterior elongation occurs, could be mistaken for a yoldiellid (Fig.44). INTERNAL MORPHOLOGY (Fig.45) The anterior adductor muscle is oval in cross section, while the posterior adductor is smaller and more elongate. Both are set in from the shell margin, the posterior is positioned at approximately two- thirds the distance between the umbo and the posterior limit of the shell. There is a small anterior sense organ formed from the sensory fold of the mantle, ventral to the anterior adductor. The siphons are joined with their ventral margins fused to form entire lumina. They are slender and particularly elongate and when contracted are con- tained in the elongate siphonal embayment. The foot and viscera lie in the anterior half of the mantle cavity. The foot is elongate and directed anteriorly. In most preserved specimens the tip of the foot lies between the anterior adductor and the shell margin. The margins of the sole are fringed with numerous relatively small papillae. There are three anterior and two posterior pedal retractor muscles. The palps and gills are markedly narrow and elongate. The are at least 22 palp ridges in the largest specimens and the palp probosci- des are attenuate each with a straight dorsal margin and a papillate ventral margin. In a few preserved specimens the palp proboscides extend from the feeding aperture. The gills are similarly attenuate Fig. 44. Propeleda paucistriata. External lateral views of the right sides of four shells of differing size to show change of shape with growth and an internal view of a right valve. All specimens taken from Atlantis II station 203 from the Angola Basin. Scale = 1mm. 130 J.A. ALLEN AND H.L. SANDERS Fig. 45. Propeleda paucistriata. a, internal morphology as seen from the right side; b, part of the left side of the same specimen to show details of the course of the gut; c, the internal morphology as seen from the left side of a much larger specimen. All specimens taken from Atlantis II station 203 from the Angola Basin. For identification of the parts see text-figure 7, p. 106. Scales = 1mm. and extend from the posterior visceral mass to the anterior limit of the posterior adductor. There are at least 22 gill plates in larger specimens. A slender extension of the axis extends from each gill from ventral to the posterior adductor to the inner junction between inhalent and exhalent siphons. From the large combined stomach and style sac the course of the hind gut takes it first dorsal and posterior to the stomach and then to the left side of the body where it makes a small loop. From there it passes ventral to the umbo to the right side of the body where it makes a much larger loop at the perimeter of the viscera and passing close to the inner face of the anterior adductor. From there it passes mid-dorsally to the anus. The mouth is set some distance posterior to the anterior adductor muscle. The oesophagus is broad and elongate and the combined stomach and style sac is positioned vertically in the posterior part of the visceral mass. The pedal ganglion is large and lies immediately anterior to the junction of mid gut and hind gut. The shell surface in some larger specimens is covered with epifaunal solitary hydroids. This would indicate that P. paucistriata lives close to the surface of the sediment. This is also suggested by the fact that the posterior tips of the shells of larger specimens are broken. We believe that this is the result of predation on the siphons. The extreme post-adductor elongation of the shell is advanta- geous in that it provides distance between predator and the more vulnerable viscera with damage being restricted to more easily generated tissue. The shell of this species differs from others described by the small number of pronounced concentric shell ridges and we name it with reference to this characteristic feature. This is the first species of Propeleda to be recorded off the south-west coast of Africa. At approximately the same latitude off the east coast of Natal a species named Leda lancetaby Boshoff (1968) occurs at upper slope depths. Nijssen-Meyer (1972) believes that this latter species is a Propeleda, and we concur with her. P. /anceta is more robust, more arcuate and with far more numerous concentric ridges than is the case in P paucistriata. DISCUSSION The major point of interest in this particular account of deep-sea protobranch bivalves is the evidence it provides to further our understanding of the evolution of the nuculanoid protobranchs. In our earlier studies on the Tindariidae we speculated as to how the nuculanoids could have evolved from the nuculoids (Sanders and Allen, 1977). In functional terms, this involved a change in the inflow of water into the mantle cavity from an antero-ventral posi- tion to a posterior position and the begining of specialization of the posterior mantle edge, a view also expressed by Yonge (1939). In the tindariids this latter involves the development of sensory papillae from the sensory fold of the mantle at the points of ingress and exit of the circulatory water. Although infaunal and deposit feeding, the tindariids, like the nuculids, live close to the surface and, like many other bivalves that occupy this position, they are ovate and robust. Many of these subsurface dwelling bivalves, including the tindariids, have stout external ligaments. The development of siphons was the next step in the evolutionary process and the neilonellids are illustrative of this. The shell form and ligamentas seen in the tindariids is largely retained in the neilonellids, but short siphons, as yet only fused dorsally, are now present and these are contained in a shallow siphonal embayment. Although the shell remains stout and ovate there is some posterior elongation and an area ventral to the inhalent siphon from where the palp proboscides are extended is more defined. Like the tindariids the neilonellids are deposit feeders living close to the surface of the sediment. DEEP-SEA PROTOBRANCHIA (BIVALVIA) The hind gut in Neilonella, like that in Tindaria, has a wide lumen and single pronounced typhlosole. Although the course that the hind gut takes in neilonellids makes a single loop on the right side of the body, it does not penetrate mantle space as it does in tindariids (Sanders and Allen, 1977). In this respect the hind gut of neilonellids probably represents the more primitive condition. We have argued elsewhere (Allen, 1992) that elongation and the complexity of form of hind gut configuration are related to food procurement at great depths, and this applies to the tindariids (Sanders and Allen, 1977). The neilonellids are for the most part upper slope species and the hind gut would be expected to be less specialized and less elongate. In Nuculana posterior elongation becomes more extreme and the ventral margins of the combined siphons are fused such that the exhalent and inhalent lumena are separate and entire. The shell remains robust, but is more slender The ligament is restricted to a small internal structure separating elongated anterior and posterior series of hinge teeth. We believe that elongation is correlated to the almost vertical orientation of the animal in the sediment but which retains contact with the surface via the extended posterior body and siphons. The genus Nuculana is found mainly in shelf and upper slope sediments and as such the available food resources are rela- tively abundant. The hind gut is not greatly extended and remains as a single loop to the right side of the body. In Propeleda the evolutionary trend of posterior body elongation seen in Nuculana becomes is more extreme, particularly posterior to the posterior adductor muscle. The posterior adductor muscle is more elongate and dorso-ventrally narrow, and the gill, gill axes, siphons and the palp proboscides are exceptionally long and slender. The shell of Propeleda, particularly in abyssal species, is much more fragile and is further specialized in that it possesses an internal posterior longitudinal ridge. The function of this ridge is not entirely clear and has await examination of the living animal but, possibly, it is involved in the separation of excretion, feeding and respiratory functions in the extremely elongate posterior mantle cavity. It may also help to strengthen the otherwise very fragile shell and assist in predation damage limition. In Propeleda post-adductor elongation involves body tissues that can be relatively easily regenerated, much in the same way as has been reported in deposit feeding tellinids (Edwards, Steele and Trevallion, 1970). Specimens showing shell repair posterior to the posterior adductor are present in our samples. The evolution of the Ledellinae and an assessment of their func- tional morphology was discussed earlier (Allen and Hannah, 1989). In respect of the species of Ledella and Tindariopsis described here, little needs to be added to that account other than to note, again, that the hind gut in these abyssal protobranchs is extraordinarily length- ened and takes the most complex courses within the visceral mass. The other item of note is the description of yet another ledellid in which the shell, after reaching a certain length, changes its direction of growth. In Ledella aberrata as in L. ultima the result of this change is to produce a broad shell margin and lateral expansion of the shell cavity. This adaptation has been construed as possibly providing more space for the gonads that begin to develop at about the time the change in direction occurs. ACKNOWLEDGEMENTS. It is fitting that in this paper we thank our numer- ous friends and colleagues, particularly French colleagues of the Biogas and Walda cruises, who provided much material and gave much advice and encouragement. We would like to mention three colleagues by name. George Hampson of the Woods Hole Oceanographic Institution and Fiona Hannah (Lonsdale) of the University Marine Biological Station, Millport, who have given us tremendous close support over the years and without their help it is likely that we would not have succeeded in this task within our lifetimes, and Kathy Way of the Natural History Museum, London, who has been so quick 131 in responding to our requests for help particularly in our quest for early literature and specimens for comparison. Much of the work was supported by grants from the Natural Environment Research Council. REFERENCES Abbott, R.T. 1974. American Seashells. Van Nostrand Reinhold, New York. Allen, J.A. 1992. The evolution of the hindgut of the deep-sea protobranch bivalves. American Malacological Bulletin, 9: 187-191. Allen, J.A. and Hannah, F.J. 1986. A reclassification of the Recent genera of the subclass Protobranchia (Mollusca: Bivalvia). 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Pp. 105— 722. £40.30 Volume 61 No. | A revised familial classification for certain cirrhitoid genera (Teleostei, Percoidei Cirrhitoidea), with comments on the group’s monophyly and taxonomic ranking. P.H. Greenwood. Studies on the deep-sea Protobranchia (Bivalvia); the Subfamily Yoldiellinae. J.A. Allen, H.L. Sanders and F. Hannah. 1995. Pp. 1-90. £40.30 No. 2 Primary studies on a mandibulohyoid ‘ligament’ and other intrabucal connective tissue linkages in cirrhitid, latrid and cheilodactylid fishes (Perciformes: Cirrhitoidei). P.H. Greenwood A new species of Crocidura (Insectivora: Soricidae) recovered from owl pellets in Thailand. P.D. Jenkins and A.L. Smith Redescription of Sudanonautes Floweri (De Man, 1901) (Brachyura: Potamoidea: Potamonautidae) from Nigeria and Central Africa. N. Cumberlidge Association of epaxial musculature with dorsal-fin pterygiophores in acanthomorph fishes, and its phylogenetic significance. R.D. Mooi and A.C. Gill. 1995. 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Drawings should be in black on white stiff card or tracing film with a line weight and lettering suitable for the same reduction throughout, either 50%, 30% or 25%. After reduction the smallest lettering should be not less than 10 pt (3 mm).All photographs should be prepared to the final size of reproduction, mounted upon stiff card and labelled with press-on lettering. Components of figure-plates should be abutted. All fig- ures should be numbered consecutively as a single series. Legends, brief and precise, must indicate scale and explain symbols and letters. Reprints. 25 reprints will be provided free of charge per paper. Orders for additional reprints can be submitted to the publisher on the form provided with the proofs. Later orders cannot be accepted. CONTENTS 71 Indian Ocean echinoderms collected during the Sindbad Voyage (1980-81): 3. Ophiuroidea and Echinoidea Andrew R.G. Price and Francis W.E. Rowe 83 Rare cyclopoid copepods (Crustacea) from Mediterranean littoral caves D. Jaume and G.A. Boxshall 101 Studies on the deep-sea Protobranchia (Bivalvia): the family Neilonellidae and the family Nuculanidae. JA. Allen and H.L. Sanders Bulletin of The Natural History Museum ZOOLOGY SERIES Vol. 62, No. 2, November 1996