126 Contributions to Indian Malacology. [No. 2> 



Ditropis.* Subg. nov. 



Testa translucens, subvitrea, epidermide olivaced nitidd instructa, 

 carinis dwabus, vel pluribus, una ad periplieriam, alter d subtus ab 

 ilia interspatio discretd circumdata. Operculum corneum, arctispirum, 

 duplex, lamina interna membranaced, externa crassiusculd, marginious 

 anfractuum liberis, ambabus sulco marginali disjunctis. Animal ig- 

 notum. 



. Shell translucent, almost vitreous, covered with a smooth olivaceous 

 epidermis, with two or more spiral ribs, one of which is always at 

 the periphery of the last whorl, and a second below, separated by an 

 interval from the other. Operculum horny closely wound, composed 

 of two lamina?., separated by a marginal groove, the inner membrana- 

 ceous, the outer rather thick, and with the edges of the whorls free. 

 Animal unknown. Type, Cyclophorus planorbis, n. sp. 



I have examined the lingual ribbon of one species. It only differs 

 from that of Cyclophorus in the form of the lateral teeth, and in their 

 denticulations being shorter and more numerous. In C. (Ditropis) 

 convexus, the species examined, the central tooth has 7 denticulations, 

 that in the middle being the largest : all the lateral teeth apparently 

 had 5 denticulations, but it was very difficult to count those in the 

 outermost laterals correctly. 



1.— Cyclophorus (Ditropis) planorbis, n. sp. 



PL XVI, fig. 1. 



Testa latissime umbilicata, depressa, discoidea, vitrea, tenuis, oliva- 

 cea, glabra, obsolete striatula, polita. Spira plana, nucleonon exserto, 

 scepe eroso, sutura impressa, ad anfractum idtimum et supra et in um- 

 bilico costd sublatd intus marginata. Anfr. 4 — 4J, convexi ; ultimus 

 antice vix descendens sub -auadr angular is, supra ataue subtus convexus, 

 carinis duabus validis circumdatus, una ad periplieriam, altera juxta 

 basin ad latus externum. Umbilicus perspectivus, omnes anfractus 

 exliibens. Apertura obliaua, sub-quadrala intus albido-labiata ; peri- 

 stoma incrassatum, rectum, non-expansum. Operculum intus convexum, 

 extus concavum, marginibios anfractuum externorum laciniatim elongatis. 

 Exempli majoris diam. maj. 8-J, min. 7, alt. 2, op. diam. If, millem. 

 „ minoris „ 7 „ 5J „ 1| „ „ (fere) U „ 



Hob. " Calcad hills," ad fines provincial Travancorc in India meri- 

 * Etym. Sis, twice ; T p 7ris, a keel. 



