On the identities of Nepinnotheres vicajii (Chhapgar, 1957) and Arcotheres casta (Antony amp; Kuttyamma, 1971) from western India: conspecificity and taxonomy (Decapoda, Brachyura, Pinnotheridae).

The identity of Nepinnotheres vicajii (Chhapgar, 1957) (described as Pinnotheres vicajii) (Pinnotheridae), a pea crab associated with the bivalve Marcia recens (Holten, 1802), is clarified. On the basis of re-diagnosis of holotype male and freshly collected female specimens from its type locality, P. vicajii is now assigned to Arcotheres Manning, 1993. A second poorly known species from India, Arcotheres casta (Antony Kuttyamma, 1971), originally collected from Meretrix casta (Gmelin, 1791) is also synonymized with A. vicajii.

New records of two sponge-associated species of Upogebia Leach, 1814 from southern India (Decapoda: Gebiidea: Upogebiidae): U. hexaceras (Ortmann, 1894) and U. nithyanandan (Sakai, Türkay amp; Al Aidaroos, 2015) resurrected from the synonymy of U. balmaorum Ngoc-Ho, 1990.

Two species of the mud shrimp genus Upogebia Leach, 1814 (Gebiidea: Upogebiidae) are recorded from India for the first time based on material from Tamil Nadu: U. hexaceras (Ortmann, 1894) and U. nithyanandan (Sakai, Türkay Al Aidaroos, 2015). Both were found in burrows in an unidentified sponge. Upogebia nithyanandan is resurrected as a valid species from the synonymy of U. balmaorum Ngoc-Ho, 1990, recently proposed by Dworschak Poore (2018). The two species are fully described and illustrated on the basis of the newly collected specimens, and diagnostic characters for species recognition are discussed.

The Ashtamudi Lake short-neck clam: re-assigned to the genus Marcia H. Adams & A. Adams, 1857 (Bivalvia, Veneridae).

The economically valuable bivalve mollusc, known as the short-neck clam, is the major fishery resource of the brackishwater Ashtamudi Lake in Kerala, India. This fishery carries a Marine Stewardship Council certification for sustainability wherein it and all hitherto published reports identify the short-neck clam or yellow-foot clam as Paphiamalabarica (Dillwyn, 1817). It is noted that this name does not conform with current nomenclature and is now correctly referred to Protapesgallus (Gmelin, 1791). Furthermore, it is shown that the identification is also incorrect. Comparative shell morphology of venerid clams of the subfamily Tapetinae from the south Indian coast demonstrates that the short-neck clam in Ashtamudi Lake is Marciarecens (Holten, 1802). Small numbers of M.opima (Gmelin, 1791) were found in Ashtamudi Lake but appear not to be part of, or contribute significantly to, the fishery. The venerid clams Protapesgallus and P.ziczac (Linnaeus, 1758) are not found in Ashtamudi Lake but are inhabitants of the shallow coastal waters of south India. Descriptions of the four confused species M.recens, M.opima, P.gallus, and P.ziczac are given. On the basis of this study, the species involved in Marine Stewardship Council (MSC) certification may be better considered at the generic level of Marcia or at the species level as Marciarecens, the most dominant species in the Ashtamudi Lake clam fishery zone.

A new species of the hermit crab genus Diogenes Dana, 1851 (Decapoda: Anomura: Diogenidae) from southern India.

A new species of the hermit crab genus Diogenes Dana, 1851, D. spongicola, is described and illustrated on the basis of material collected from two locations off southern India. It appears close to D. takedai Rahayu, 2012 among about 70 congeners, but easily differentiated from the latter by the spinulose anterolateral margins of the shield, the article 2 of the antennal peduncle armed only with one distal spine, the longer, spinose antennal acicle, the absence of prominent spines on the ventrolateral margin of the cheliped meri, and the different color of the cheliped palm. Specimens of the new species were all collected from cavities of a callyspongiid sponge Callyspongia diffusa (Ridley, 1884), suggesting a possible association between the hermit crab and sponge.

Conidae (Mollusca, Gastropoda) of Lakshadweep, India.

Lakshadweep, the northernmost region of the Chagos-Maldives-Lakshadweep group of islands located southwest of the Malabar coast of India in the Arabian Sea, is the only chain of coral atolls in India. This paper documents the diversity of the molluscan family Conidae from the seas around all ten inhabited islands of Lakshadweep. Of the 78 species of cone snails now reported from Lakshadweep, 49 were recorded in this study. Three of these had not previously been reported from India, and four are newly reported from Lakshadweep. The results increase the number of Conidae species known from Lakshadweep by 10%.

A new large oregoniid spider crab of the genus Pleistacantha Miers, 1879, from the Bay of Bengal, India (Crustacea, Brachyura, Majoidea).

A new species of deep-water oregoniid spider crab of the genus Pleistacantha Miers, 1879, is described from the Indian Ocean. The species is distinct in possessing a prominently inflated carapace in which the median parts of the branchial regions almost meet. It can also be distinguished from its closest congeners, P. moseleyi (Miers, 1885), P. pungens (Wood-Mason, in Wood-Mason & Alcock, 1891), and P. ori Ahyong & Ng, 2007, in its more elongate and less spinose chelipeds and ambulatory legs, shorter third maxilliped, trapezoidal male pleon and a male first gonopod which is relatively stout with a short subdistal dorsal papilla.