218 F. Stoliczka — Notes on Terrestrial Mollusca. [No. 3, 



comparison of the two will no doubt prove interesting, and estab- 

 lish, more firmly the relations of the present genns to Gorilla, 

 Ophiogyra, and the American Polygyra. 



The Indian and Burmese species referable to Plectopylis are : 

 P, achatina, Gray, P. anguina, refuga and repercussa, Gould, cyclas- 

 pis, brachyplecta, plectostoma, leiophis, pinacis, Bens., Karenorum, 

 perarcta, Andersoni and macromphahis, Blf., a new species allied to 

 the last from the Khasi hills, and probably also Helix reiifera, Pfr., 

 another species from Ceylon, and also H. pettos* of Martens, 

 apparently closely allied to PI. pinaci?. All the species characterize 

 the Malay fauna ; none of them occurs westward of Sikkim, and 

 their geographical distribution extends from this part of the Hima- 

 layas, in a south-easterly direction through Assam, the Khasi and 

 Tippera hills into Burma, Tavoy and the Southern Malay country. 

 Only the last mentioned species is found on the Nilgiri hills, its 

 form represents a slightly different type, the umbilicus being com- 

 paratively narrower than in any other Plectopylis, and the margins 

 of the aperture are barely expanded ; within there is only a trans- 

 verse ridge on one side projecting between two pairs of tubercles on 

 the other ; no longitudinal ribs are present. I fully expect that, when 

 the animal of IT. retifera becomes known, it will probably exhibit 

 somewhat different characters from those of the present genus. 



The shells of Plectopijlis are characterized by a planorboid, 

 umbilicated form, somewhat expanded and usually thickened 

 peristome, and by the presence of one or two transverse, and a few 

 spiral ridges placed internally some distance from the aperture. 

 I consider these internal folds to be in some respect analogous to 

 the clausilium in Clausilia, the animals of the two genera being 

 also somewhat similar in external characters. When the animal 

 of Plectopylis retracts into its shell, the passage through the folds 

 is generally found to be filled up with mucous secrection, but the 

 body itself mostly retracts one half of a whorl further inwards. 

 During hibernation the aperture is besides closed with the usual 

 calcareous lamina, as in other Helicid^e. 



I have examined the animals of PI. achatina, cyclaspis, pinacis, 

 and macromphalus. They are all very similar in external shape 

 * Malacozool. Blastter, xv, p. 158. 



