414 Records of (he Indian Museum. [Vol. XVI, 



shell-characters, hi the genus Lithoglyphus. He was acquainted 

 with the peculiarities of the radula to which we will refer later, 

 but did not consider them of generic importance. In 1889 Heude 

 erected a new genus {Fenouilia) for what we believe to be 

 thfe same species. He was apparently ignorant of Neumayr's 

 description and called the form F. hicingulata. This species was 

 described for the third time in 1904 by Fulton under the name 

 Jullienia carinata. The shell is very hke that of Lithoglyphus 

 but differs in the shape of the mouth (which is not shown quite 

 correctly in Neumayr's figures) ; from Jullienia it differs in its thin 

 outer lip. 



The genus Paraprososthenia , or rather the only known recent 

 species, was identified by Neuma3^r with the fossil genus Prosos- 

 thenia. The latter is only known from the Miocene beds of Eastern 

 Europe, while the living species inhabits Lake Tali Fu, in which 

 P. coggini was also found. The fossil shells differ, however, in 

 their thick outer lip and the resemblance is probably conver- 

 gent. The subgenus Parapyrgula resembles the recent and fossil 

 genus Pyrgula of Central Europe and the eastern Mediterranean 

 basin in shell-characters, but has not quite the same type of 

 sculpture and again differs in the distinctly pyriform shape of 

 the mouth. Except in its very small size and delicacy of structure 

 it closely resembles the shell of the N. American Goniobasis, the 

 most prolific in species of the Pleuroceratid genera and the onl}^ 

 one of which the geographical range extends to the Pacific coast of 

 North America. 



This resemblance in the outward form of the shell between 

 Parapyrgula and Goniobasis would not be sufficient in itself to 

 establish family identity, and in Fenouilia evidence of the kind is 

 weak depending as it does on a much less marked resemblance 

 between the shell and that of Anculosa. The operculum of the 

 two Chinese genera might equally well belong to the Hydrobiidae, 

 to the Melaniidae or to the Pleuroceratidae. It is only when we 

 examine the radulae that definite affinities begin to manifest 

 themselves. According to Troschel's ' figures the radulae of the 

 Pleuroceratidae resemble those of the Melaniidae rather than those 

 of the Hydrobiidae. The central tooth is small and transverse 

 and its disc is without latero-basal denticulations or other projec- 

 tions. The tooth on either side of the central tooth differs greatly 

 from the two outermost teeth and the dental formula would seem 

 to be 2. I. I. I. 2. The lateral tooth is characterized by the large 

 size of the central denticulation. According to Stimpson * this 

 feature is characteristic of the family as a whole, but Walker '^ in his 

 recent synopsis of the N. American freshwater molluscs lays stress 

 on the absence of basal denticulations on the central tooth. 



t Das Gebiss dey ScJineeken I, p. 109, pi. viii, figs. 7-9 (Berlin : 1856-63). 



2 For an account of certain features of the anatomy of the Pleuroceratidae see 

 Slimpson, Amer. Joiirn. Sci. (ij XXXIII, pp. 41-63 (1864). 



3 In Ward and Whipple's Fresh-water Biology, p. 091 (New York: 1918). 



