1869.] Contributions to Indian Malacology. 131 



known forms in the combination of characters presented, that such 

 appears the only course open, and as will be seen presently, the 

 characters of the lingual dentition fully bear out the separation. 



Cyclophorus (Ditropis) convexus. Mychopoma limbiferum. 



Mychopoma* gen. nov. 



Testa in speciebus notis turbinata epidermide fused, crassd hirsutd 

 induta. Apertura intus corrugata. Operculum simile ei generis 

 Opisthopori, e duobis discis multispiris, parallelis, interno membranceo 

 externo calcareo compositum ; lamina spirali erectd interpositd inter- 

 spatiis vacuis. 



Shell, in the two species hitherto known, turbinate, cover- 

 ed with a thick dark-coloured epidermis, more or less hairy. 

 Aperture crenulated within. Operculum very similar to that of Opis- 

 thoporus in structure, composed of an external calcareous and an 

 internal membranaceous layer, both multispiral and united by a spiral 

 lamina at right angles to them, the spaces between the whorls of 

 which are vacant. The operculum is flat or nearly so, rather thick, 

 and with a marginal sulcation. 



Of this type also I have examined the lingual dentition of one 

 species, 31. limbiferum. The central tooth much resembles that of 

 Cyclophorus in form, but it has 7 nearly equal denticulations. The 

 inner lateral teeth are much broader, and differently placed from those 

 in any other Cyclophoridae which have been, so far as I know, ex- 

 amined. They also have 7 denticulations, and the same appears to be 

 the case in the outermost laterals, on which, however, it is difficult to 

 count the exact number. These outermost teeth differ greatly in form 

 and position from the usual type amongst the Cyclophoridce, and rather 

 resemble those of Paludina or Valvata. 



* Typns M. hirsutum, Be.ddome, MS. Etyni. ^u.i;^os an inner chamber, -n-wiia 

 operculum. 



