I92I.] 



B. Prashad : Notes on LamclUbranchs. 



139 



often weathered and wormed in fnlly grown specimens, greatly- 

 recurved anteriorly and separated from one another by a narrow 

 chink only ; lunule well marked rather narrow but deep ; ligament 

 prominent but not very thick, about thrice as long as the lunule. 

 Hinge in general facies quite similar to that of C. ceylonica, but 

 much more curved and with the lateral teeth more delicate though 

 comparatively much longer ; the cardinal teeth more slanting, 

 stouter and not so deeply bifid. 



Mcasuyements (in millimetres). 



Distribution. — Clessin was certainly wrong in including the 

 East Indies in the range of distribution of this species, as it is 

 confined to Bengal onlv. In Bengal the specie= is fairly common 

 in the estuarine areas of the Gangetic Delta and is burnt in large 

 quantities for making lime. It is probably the species referred to 

 by Benson as C. siiniatranci from the Sunderbans.' 



Remarks. — The spscies is distinguished from the other Indian 

 species of the genus bv its shape, the concave anterior border and 

 the greatly recurved umbones. 



Cyrena siamica, Prime. 

 Plate XX, figs. 3—5. 



1861. Cyrena siamica. Prime. Pi-oc. .Acad. ^at. Sci. Philadelphia, p. 



126. 

 l66v Cyrena siamica. Prime. Cat. Corhictilidae, p. 6. 

 1864. Cyrena siamica. Prime, .Ann. Lyceum Nat. Hist. New York. 



'VIll,. p. 86, fig. 35. 

 i86g. Cyrena siamica. Prime, Cat. Corbicididae in Amer. Jourii. 



Conch. V, p. 1 4.7. 

 1879. Cyrena siamica, Clessin, Cycladeen in Martini-Chemn. Condi. 



Cab., p. 123. pi. xix, fig. 4. 

 1897. Cyrena siamica, von Martens, Siiss. und Brackiu. Moll, in 



Weber's Zool. Ergeb. Nieder. Ost. hid. W , p. 91. 



Two separate valves from Rangoon, Burma, two specimens 

 from the Nicobars, one from Cochin-China and one from Cam- 

 bodia in the Indian :\Iuseum collection belong to this species. 

 The Nicobar and Cambodian species were found labelled C. sunia 

 trensis, but they differ from the true sumatrcnsis in the shell 

 being less tran verse, less inflated, the hinge more curved and 

 broader, all the teeth stouter and the laterals much more solid and 

 curved, the umbones less prominent and not so recurved and in 

 colour. 



I have nothing to add to Prime's description of the species, 

 but give below measurements of the various specimens in the 



Benson, Journ. As. Soc. Bengal \'ll, pt. 1, p. 4-' (1838). 



