Indosphenia abbreviata chilkaensis (Preston, 1911)

Oliver, P. Graham, Hallan, Anders, Jayachandran, P. R., Joseph, Philomina, V. F. Sanu, & Nandan, S. Bijoy, 2018, Taxonomy of myid bivalves from fragmented brackish-water habitats in India, with a description of a new genus Indosphenia (Myidae, Myoidea, Myidae), ZooKeys 799, pp. 21-46 : 33

Indosphenia abbreviata chilkaensis (Preston, 1911)

Corbula chilkaensis Preston, 1911: 39, fig. 2; Subba Rao 2017: 432.

Cuspidaria annandalei Preston, 1915: 308, figs 23, 23a; Ramakrishna and Dey 2010: 303-4; MolluscaBase 2018d.

Type material examined.

Corbula chilkaensis . Type material was not available for study.

Cuspidaria annandalei . Syntypes, 3 shells, Lake Chilka [this can be interpreted as 19°42.9'N, 85°18.6'E]. Ex Preston, NMW.1955.158.18922-18923.

Type localities.

Corbula chilkaensis . "Rambha, S. end of Lake Chilka" [this can be interpreted as off Rambha approximately 19°31.2'N, 85°6.3'E].

Cuspidaria annandalei . "Lake Chilka, 4-9 miles E. by S.1/2 S. of Patsahanipur, 4-5 ft" [this can be interpreted as off Patasanipur approximately 19°42.9'N, 85°18.6'E].

Remarks.

Examination of shells (Fig. 5 k–m) of Cuspidaria annandalei shows these to be identical with small specimens of the typical Port Canning form, including the presence of radial striations on the prodissoconch. Lake Chilka, some 55 km in length, is situated in the northern part of the Bay of Bengal approximately 400 km south-west of Port Canning and is largely isolated from the Bay of Bengal by a long shore bar, only connected by a channel less than 2 km wide. For the moment, and based on significant morphological similarities, we regard all of the taxa from the northern part of the Bay of Bengal to be a single species, taking the name of Indosphenia abbreviata (Preston, 1907), with the Lake Chilka population herein deemed a subspecies. However, we note that future molecular study may suggest genetic divergence not readily apparent based on shell morphology.