130 Contributions to Indian Malacology. [No. 2, 



a generic character of higher importance than the structure of the 

 operculum, so much so, that I believe, as I pointed out in 1864,''' 

 that Opisthoporus can only rank as a sub-genus of Spiraculum, 

 Pearson, which has a totally different operculum but a similar sutural 

 tube. The similar structure of the operculum in the species lately dis- 

 covered in the hills of Southern India, by no means serves to prove 

 any very close affinity to Opisthoporus, since the characters of the 

 shell are totally distinct. With the exception of the absence of the 

 sutural tube, this is not the case with Cyclotus variegatus and its 

 allies. I do not think the present forms would have been classed by 

 Mr. Benson in the same genus as Opisthoporus, and as I am in- 

 clined, after a good deal of study of the Cyclophoridce, to consider the 

 opercula alone as quite insufficient for the foundation of generic 

 groups, and to attach far less importance to their characters than has 

 hitherto been done by Mr. Benson and Dr. Pfeiffer, I am even less 

 disposed to class together dissimilar shells solely on account of the 

 opercular structure than those naturalists are. 



The operculum of the new genus appears to me, despite its resem- 

 blance to that of Opisthoporus, to be a modification of a slightly differ- 

 ent type. That of Opisthoporus is produced by variation of the 

 typical Cyclotus operculum, but with less closely connected whorls. 

 That of the genus now proposed, I consider a modification of the 

 Cyathopoma operculum, in which the calcareous outer edges of the 

 whorls, instead of being merely slightly curved towards the centre 

 and free, are so much more curved that the outer edge of each joins 

 the next interior one. Another modification of the same occurs in 

 Jerdonia, in which the same outer edges are lamelliform and flat, 

 each overlapping the inner one. 



Undoubtedly all these numerous forms of Cyclopihoridce are very 

 puzzling. The types of land Mollusca are after all few compared 

 with those of most other forms of terrestrial animal life, and the 

 tendency to variation amongst them is excessive, and in the Cyclo- 

 phoridce especially, the operculum has evidently become a very variable 

 portion of the organism. It is very difficult to determine, in a case 

 like the present, whether it is wise to found a new group or not. 

 Still the two shells now to be described differ so much from all other 

 * Ann. and Mag. Nat. Hist. Ser. 3, Vol. XIII. p. 451. 



