246 Records of the Indian Musetiui. [Vol. XVI, 



ish profusel}^ spotted with dull purplish-brown. The spots are 

 transversely elongate in the lower parts of the whorls, and often 

 alternate with shorter spots of a whitish colour. Towards the 

 upper part of the three lowest whorls the dark marks tend to 

 take the form of longitudinal streaks nearly as broad as the pale 

 interspaces. 



The most striking feature of the radular teeth (fig. 2&) is 

 that the central cusp of the central tooth is verv large, with a dis- 

 tinct lateral cusp on either side ; the thicker more prominent part of 

 the former extends right across the cusp and occupies more than 

 one half of its area. Most of the denticulations of all the teeth 

 are transversely striate. 



The species is only known from the lower parts of the Gan- 

 getic Delta. 



Littorina delicatula, Nevill. 

 (Plate XX, fig. 4). 



1884. Littot'i)ia*coi!ica var. delicatula, Nevill, op. cit., p. 150. 



The shell of this form is thinner than that of any other spe- 

 cies of the genus we have examined, and is always very brightl}'^ 

 coloured when fresh. The colours, however, as Nevill has noted, 

 are somewhat evanescent. The columella is shorter than in 

 L. suhintermedia and the longitudinal depression upon it is much 

 less well defined. The body-whorl is distinctly angulate in adult 

 shells owing to one of the ridges being much more strongly devel- 

 oped than the others, but as this ridge is situated not very far 

 from the anterior margin of the whorl, it is not found in young 

 shells. 



We figure the radular teeth (fig. ic). The central tooth is 

 smaller than in the other two species we have discussed ; its cen- 

 tral cusp somewhat resembles that of the central tooth of L. 

 melanostoma. but is much smaller, and has the membranous mar- 

 ginal portion less well developed. The inner lateral is nmch more 

 symmetrical. 



This species, like the last, is apparently endemic in the lower 

 parts of the Gangetic Delta. The two are often found together on 

 trees and bushes far above high- tide mark. The}^ seem to be very 

 largely terrestrial in habits. 



Family HYDROBIIDAE. 



Genus Stenothyra, Benson. 



This is one of the most characteristic genera of the upper 

 estuarine waters of South-eastern Asia. It is often found in fresh 

 water, but rarely in places permanentl}' unaffected by tidal influence. 

 Both the species here described are from water that was quite 

 fresh at the time of their capture, but is slightly brackish at other 

 seasons. 



