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



tween the species and Cremnoconchus. . ." and proceeds to describe 

 the var. airta. 



" The specimens I have examined particularly were collected by 

 m3'self at the edge of a tank near Bangalore some years ago. The}' 

 belong to the var. curta, Nevill, and differ from the typical form 

 not only in being rather shorter, with the spire less exserted, but 

 also in having a chestnut-brown epidermis. The operculum is 

 sub-circular or broadly ovate. It differs considerably from that of 

 any species of Bithynia with which I have been able to compare 

 the specimens, but closely resembles that of the new genus 

 Pseudovivipara from China which I am descibing in the " Memoirs 

 of the Asiatic Society of Bengal." * Externally it is covered with 

 a thick brownish epidermis and varies considerably in appearance 

 in accordance with the age of the specimen. In large shells it is 

 always more or less eroded, and there are as a rule at least two 

 areas marked off by concentric ridges. The centre is always 

 concave and numerous concentric striae can be detected on the 



surface if it is not eaten away. 

 The nucleus is small and has 

 a slight indication of spiral ori- 

 gin. The substance of the 

 operculum is calcareous and, 

 though not very thick, white 

 and porcellaneous. The inner 

 surface is convex and smooth, 

 without sculpture. It has a 

 raised margin forming the out- 

 er wall of a rather deep peri- 

 FiG. ^.-Mysoria costigera (Kiisier) pheral groove. This raised 

 var. cufta {'^Qv\\\). margin is, however, very deli- 



Radula teeth, x 250. cate and apt to be destroyed 



in removing the operculum. 

 The radula in general structure resembles that of Bithynia, but 

 the central tooth differs in three important points: — (i) there are 

 no basal denticulations, (2) there is a single lateral denticulation on 

 each side, connected by a continuous ridge with a central promi- 

 nence on the disk of the blunt finger-shaped tooth, (3) the base of 

 the tooth is turned upwards in the middle to form a broad process 

 directed opposite to that of the anterior denticulations. The central 

 tooth is very small compared with the others. 



These features of the radula and operculum probably indicate 

 that the species should be made the type of a new genus. Unfor- 

 tunately the soft parts of my specimens are not sufficiently well 

 preserved to show an3'thing except that the foot is relatively short 

 and certainly not bifid." 



This radula is a very different one to that of Bithynia tentaculata 

 (fig. 4), which I have looked at and drawn. It shows beyond 

 doubt the generic value of Mysoria. A glance at the central tooth 



' Annandale, Mem. As. Soc, Bengal, VI, pp. 309-312, pi. x, figs. 3, 3a (1918J. 



