192 1. J Mampuy Molluscs. 587 



and the bases. The snout is dark with an irregular stripe of pale 

 specks running forward from each e5^e. 



The radula is of the same type as that of C. hirasei and C. 

 subspiiiosum, and has the formula approximately 12. 9. 1.9. 12. 

 The external marginals are very feebly developed. The jaw con- 

 sists of a small central piece, which is rather narrow and deep, and 

 two lateral pieces, each of which is very long and thread like. 

 The whole jaw is feebly chitinized. The internal anatomy is of 

 the Planorbid type, but it is im.possible for us to go into details 

 owing to only two specimens being available. The penis-sheath, 

 however, is broad and stout with a small penis, without any sty- 

 let at the end. 



Walker's figures of C. hirasei show the anal siphon, slightly 

 clavate tentacles and (in a highly contracted state) the left epi- 

 podial lobe. They provide no evidence of any generic difference 

 between the species with elongate shells and C. linealum, in which 

 the type of shell-form is much less extreme. As we have shown 

 in another paper (op. cit., p. 28) a species (C. subspinosum) occurs 

 in Kashmir with a shell in some respects intermediate between 

 the two types. We see no reason, therefore, to separate C. linea- 

 tum genericalh" from Caniptoceras. 



Two specimens of this species were found crawling on the 

 underside of floating grass-stems in a small, sluggish muddy 

 stream that runs into the north end of the Loktak l^ake near 

 Potsengbam. They were accompanied by numerous individuals 

 of Ancylus viola. Though their progression was slow and An- 

 cy^MS-like, doubtless on account of their small foot, tliey showed 

 great nimbleness in twisting the free part of the body about in 

 the mouth of the shell. They remained submerged when placed 

 in a vessel of clear water. The only other specimens of this 

 species were found many years ago by Col. Godwin- Austen in 

 what is now the Dacca District of Eastern Bengal. They were 

 aestivating in dry weather among herbage at the edge of a partly 

 desiccated pool and had secreted an epiphragm inside the mouth 

 of their shells. Though the structure still remains intact, after 

 nearlj' half a centur}', in specimens in Calcutta and London, the 

 soft parts of the animal, at any rate in Calcutta, have completely 

 decayed inside it. 



Family ANCYLIDAE. 



The taxonomy of this family is rendered difficult by the 

 simple, probably degenerate character of the shell and by the 

 habitual smallness of the animals. Walker, in recent volumes of 

 Nautilus, has gone to great lengths in separating the species into 

 genera and even subfamilies on microscopic characters largely in 

 the radula. His classification is, however, impossible to apply 

 without much labour and some residue of doubt in many cases. 

 Some of the genera he recognizes are undoubtedly distinct, but 

 the separation of " Ferrissiinae " from the Ancylinae is fraught 

 with more danger than perhaps its intrinsic merit justifies, for the 



