192 



striae; dorsal margin anteriorly gradually sloping, posteriorly 

 arched and more rapidly descending ; ventral margin somewhat 

 straight ; anterior side rounded ; posterior side angled above and 

 below, somewhat obliquely and obtusely rostrate; hinge teeth 



Fig. 24. 1 & 2. Lamellidens (Z/,) mainwariiigi, Preston. (Type.) Nat. size. 

 3. Hinge of same. 



well developed, moderately short ; anterior adductor scar deeply 

 impressed ; posterior scar somewhat roughly triangular, well 

 impressed ; interior of shell bluish iridescent, rather granulate. 



Long. 25*5, lat. 50 mm. 



Hob. Siliguri ; there are also specimens in the Indian Museum 

 from Namtsik, Dihong Biver. 



Type in the Indian Museum. 



A small, light, and thin form, which Simpson in his * Synopsis 

 of the Naiades ' * refuses to recognise as a species, but regards as 

 L. consobrinus ; the author, however, having been able to examine 

 a large series from the collection of the Indian Museum, all the 

 specimens of which are very constant in their size, form, and 

 hinge, and other characters,, considers it without doubt to be 

 worthy of specific rank. 



The following dimensions are taken from specimens in the 

 Indian Museum Collection : 



* Washington, B.C., Smiths. Inst., Nat. Hus. Proc. xxii, 1900, p. 856 

 (footnote no. 3). 



