1836.] Fluviatile Shells from Sylhet. 351 



nal of the Asiatic Society for January 1832, pp. 13 and 76, and which 

 I altered to that of Tanychlamys in a paper on the genus read before 

 the Zoological Society in August 1834. Mr. Gray's characters, 

 drawn up from specimens preserved in spirits, and from General 

 Hardwicke's drawings, having the advantage of priority of publica- 

 tion, his name, although inexpressive, will necessarily be adopted. 

 Several independent observers have united in stating the necessity of 

 separating this genus from Helix, on the characters of the animal ; 

 witness the observations of Lieut. Hutton, Journal of the Asiatic 

 Society, vol. iii. p. 83. 



The species under review differs from N. vitrinoides in sculpture, 

 has a more exserted spire than the generality of specimens of that 

 shell, has a more angular periphery, is of a lighter colour, and, pos- 

 sessing the same number of whorls, is larger and of a thicker substance. 

 The epidermis is apt to peel off the under side. 



I have a third species belonging to this country, which I lately 

 took at the foot of the Rajmahal hills. It differs in its smaller size, 

 its lighter colour, and in the form of the aperture from both vitri- 

 noides and decussata, and from the former it altogether differs in its 

 habits even when inhabiting the same spot, abounding on shrubs and 

 bushes, while N. vitrinoides is confined to the ground, to rocks, and 

 to brick work. 



3. Helix plectostoma. Testa reversa, depresso-conoidea subtus 

 tumida ; spira exsertiuscula ; anfractibus supra planatis, radiatim pli- 

 catis, rugis transversis decussatis ; ultimo angulato, angulo subtus 

 marginato. Apertura lunata, plica, (ut in Helice personata) interdum 

 inconspicua, ultimo anfractui adhserente ; umbilico profundo, anfractus 

 plerosque exhibenti. Diam. 0.35 poll, paulo plus. 



This shell has a salient plate on the penultimate whorl connecting 

 the two extremities of the peristome, as in H. personata, but differs 

 from it in its other characters. The peristome is more rounded than 

 in H. Cocyrensis, the spire more conoid, and the satures less conspi- 

 cuous. It belongs to the subgenus Helicodonta of De Ferussac, but 

 in the angularity of the periphery it approaches to Helicigona. 



4. Helix Oxytes. Testa ferrugineo-cornea, depressa ; spira, con- 

 vexa, apice planato ; periphseria. acuta ; anfractibus oblique subplicatis, 

 suturis non excavatis ; peristomate subreflexo ; umbilico lato et pro- 

 fundo anfractus usque ad apicem exhibenti. Diam. 1.8 poll. 



In form it exactly resembles H. acumen of Dalmatia, but exceeds 

 it in size, and differs in colour, in its sub-reflected mouth, and in 

 sculpture, the whorls being destitute of decussating striae and of the 

 polish which adorns the latter. It belongs to De Ferussac's groupe 



