ii2 



Records of the Indian Museum. 



[Vol.. XIX, 



cesses ^ on the extreme edge of the mantle in the young. In those 

 species in which the shell of the adult possesses smooth spiral ridges 

 of a dark colour (notably Vivipara oxytropis) the processes per- 

 sist in the adult, but in those that have smooth unicolourous shells 

 they become small and inconspicuous or disappear altogether. In 

 Taia, in which the spiral ridges are never quite smooth, but as a 

 rule nodular, squamdse, or even spinulose, there are no such pro- 

 cesses in the adult, and they are also absent in the somewhat simi- 

 lar Chinese genus Margarya ; but apparently temporary lobes of 

 the mantle-edge can be thrust into the small concavity at the base 

 of each nodule, scale or spine. I hope to elaborate this point on 

 another occasion. 



Genus Vivipara, Montfort. 



This genus is so well known that 

 full description. The Indian species 



it is unnecessary to give a 

 fall naturally into four 



-b.s. 



Vertical sections through the inantle-edge of Inchan Vivipariclae. 

 I. Vivipara oxytropis. 2. Taia intha. 3. LecytJioconcJia lecytliis. 

 b.s. blood-space; l.m. longitudinal muscle, sp. transverse sphincter. 



groups, which may be named after the type-species of each as 

 follows : — 



ViviPARAE BENGAi^ENSES. The shell is normally of moderate 

 size, occasionally large, as a rule thin but thickened in certain 

 phases. The whorls of the spire are not greatly swollen and the 

 suture is not deeply impressed. The outline is ovate, but varies 

 considerably. Spiral bands darker than the rest of the shell are 

 always present, though sometimes obsolescent. They are never 

 very numerous and vary considerably in breadth. In some forms 

 these bands become thickened to form ridges and there is often a 



i I can find no reference to these processes in the European forms. Er- 

 langer {Moipli. Jahrh.., XVII, pi. xxii: 1891), and other authors figure the edge 

 of the mantle in the fully formed embryo as smooth. 



