1919-] H. H. Godwin- Austen : Fossaruhis in India. 



213 



shows how distinct the two genera are. They cannot be placed in 

 the same family. If the living animals of the Palaearctic and 

 South Indian species could be looked at side by side I imagine they 

 would differ considerably one from the other. In drawings of 

 Bithynia teniaculata I made many years ago, the tentacles are shown 

 to be very long and finely pointed. 



A figure of the radula of this species, the type of the genus, 

 is given by Dr. Paul Fischer in Manuel de Cnnchyliologie, p. 723 ; 

 he alludes to and shows what he calls "basal denticulations." 

 These are rather nearer to the marginal edge of the tooth, a folding 

 over of the same, and would appear to represent lateral cusps — an 

 indication I think I have seen put forward by some writers that 



Fig. 4. — Bithynia tentaciilata, Linn. 



a. Centre and adraedian teeth of radula, x 360. In the first are seen the 

 " basal denticulations" representing the marginal cusps by the folding over of the 

 margin: in the second the teeth are seen from the side. 



b. The two marginal teeth, x 360. 



the central tooth of these operculates was orginally a series of sepa- 

 rate teeth now merged together. 



The radula of other species of Indian Bithynia, that of kashniir- 

 ensis for instance, should be looked at; they may not all be 

 like that of B. tentaciilata. Dr. Annandale has kindly sent me for 

 perusal his valuable notes on ' ' The Aquatic MoUusca of the Inle 

 Lake and connected waters, Shan States." He includes the species 

 collected of Nevill's genus Hydrobioides. He says the radula is 

 like that of Bithynia, but with no further detail. This, however, is 

 made good by excellent figures of the radulae of H. nassa, Theobald 

 and two new species (plate xiv, figs. 4, 4a ; 2c ; and 5). These show 

 the basal denticulations of the central tooth, so typical of Bithynia, 

 present in every case; they are 3 in number, fewer than in B. 

 teniaculata , in which 4 or 5 are present. 



