244 Records of the Indian Museum. [Vol. XVI, 



Malabar coast, and from a small stream twenty-eight miles east of 

 that place. 



We figure (fig. la) the radula of a specimen from the Hugli. 

 Both the lateral and marginal teeth differ considerably from those 

 of the next species ; the marginals being considerably smaller and 

 having the denticulation stronger. The differences between the 

 laterals are of a very complicated nature, and will be understood 

 best by a reference to the figures. 



Dostia platyconcha, sp. nov. 

 (Plate XX, figs. I, 2c). 



This species differs from both the other Gangetic forms and 

 from all others of the genus known to us in its much thinner and 

 more transluscent shell, its depressed form and non-protruding 

 spire. Its lateral profile is regular and forms an arch, less than a 

 semicircle; the spire hardly protrudes beyond the anterior margin 

 of the body-whorl. The spire though very minute is, however, 

 distinctly lateral and spiral. In ventral view the shell is broadly 

 oval, slightly truncated posteriorly. The upper part of the shell is 

 invisible or practically invisible in this view. The columellar 

 plate is separated from the lower margin of the shell, and extends 

 considerably more than half way across its true mouth. The 

 margin is irregularly and minutely crenulated. The posterior lip 

 is very broad below the anterior margin of the true mouth of the 

 shell. The dorsal surface is marked with well defined and regular 

 transverse striae ; minute longitudinal striae can also be detected 

 with a strong lens. The periostracum is dull olivaceous green 

 with minute black specks and with obscure longitudinal rays. 

 The interior of the shell including the columellar plate has a faint 

 glaucous tinge and is very highly polished. 



The operculum is rather short and instead of bearing a single 

 prominent lateral process has two short rather broad tubercles 

 one of which may be obscure. 



We figure the radular teeth (fig. ib). 



Type specimen : M ^^^^ in the collection of the Zoological 

 Survey of India. 



Locality. — The species is not uncommon in the lower parts 

 of the Gangetic Delta, on bushes at the edges of creeks containing 

 brackish water of considerable salinity. 



Family LITTORINIDAE. 



Genus Littorina, Ferussac. 



A number of species of this genus lead an amphibious or 

 almost terrestrial existence on the banks of the waterways in the 

 lower part of the Gangetic Delta. At present we will deal with 

 only three of these, namely L. melanostoma , Gray, L. subinter- 

 media, Nevill and L. delicaiula, Nevill, 



