124 Records of the Indian Museum. [Vol. XI V, 



Burma. The shells of these remarkable species exhibit affinities both 

 with Viviyara {s.s.) and with Margarya, Nevill ; they also have some 

 resemblance to those of Tulotoma, Haldeman. 



The genus may be defined concisely as follows : — 



Shell conical-ovate, conoidal or conical, varying greatly in thickness 

 but never excessively thick and often quite thin, with coarse longitudinal 

 striae and strong spiral ridges usually of a granular, nodular or squamous 

 structure ; at least three such ridges present on the basal whorl ; whorls 

 7 to 8 ; spire well-developed, often produced but never cylindrical ; 

 aperture of shell sub-triangular, often contracted above ; colmnellar 

 callus very broad and thick, extending over the umbilicus in the form of a 

 convex ridge or flat plate ; operculum nearly as large as aperture of shell, 

 horny, pyriform, concave on the external surface, and with a strong 

 ridge along the inner margin, with the muscular scar relatively large 

 but not very thick, with at any rate the outer margin membranous. 

 Radular teeth elongate, with the terminal denticulation strong, with a 

 well-developed lamellar process on the tip of the central and lateral 

 teeth. Anatomy of the soft parts as in Vivipara. 



Type-species : Vivipara naticoides. Theobald. 



I assign to this new genus eleven species from the Shan Plateau ; 

 also Vivipara noetlingi, Kobelt, from the Lower Chindwin district of 

 Upper Burma and an undescribed species from Ava on the Irrawaddi 

 which I only know from a single broken shell. Of the Shan species 

 six are extinct. 



In describing a new genus and so many species I have followed the 

 course that seemed most convenient. In the first draft of this paper 

 I adopted a trinomial or rather quadrinomial system, but not only 

 did I find myself constantly tripping over the names, but in several 

 instances could not be quite sure to which species to assign a subspecies. 

 Moreover, between the different sets of specimens that I had proposed 

 to regard as representing distinct races or varieties I found constant 

 differences in the form of operculum and in the proportions of the radu- 

 lar teeth, in all instances in which it was possible to examine these 

 structures. 



The development of the columellar callus, which sometimes extends 

 from the aperture across the whole of the lower surface of the inner 

 part of the body-whorl, is the most constant feature of the genus, and 

 distinguishes it from Margarya and also from Tulotoma. This con- 

 stitutes a resemblance to the Chinese genus Rivularia, Heude, but in 

 other respects the structure and form are very different. From Tulo- 

 toma, Taia is also differentiated by the structure of the prominences 

 on the chief spiral ridge of the body-whorl. My friend Mr. G. H. 

 Tipper of the Geological Survey of India has been kind enough to cut 

 sections of shells of Margarya melanioides, Tulotoma magnificat and 

 Taia lacustris for me. In transverse sections of the Tulotoma shell, 

 the prominences on the chief ridge of the body-whorl appear to be com- 



* For figures of tliis shell, which is apparently somewhat vaiiable, see Kiister's Mono- 

 graph of Paludina, etc., in CAeww*/2'« Towc/s. Cub., p. 23, pi. V, figs. 3-D (1852), T. 

 mngnifira lives on stones in the Alabama river. It is the only known living species of 

 its genus. 



