12 Account of a new Genus of Land Snails, [Jan. 



Habitat in rupibus umbrosis Patharghatae et Sikrig di. 

 Shell discoid, somewhat convex above, concave below, and widely 

 umbilicated ; whorls cylindrical, slightly adhering together, and visible 

 on both sides. Sutures channelled. Peristome reflected, interrupted 

 at the summit of the aperture by an oblique sinus. Outer lip furnished, 

 at the upper part, with an arched wing, which overhangs the sinus. 

 Wing broad, tumid, bending downwards, and mucronate in front, 

 adhering to the penultimate whorl. 



This new form I dicovered on the 15th and 16th December, 1831, 

 among the jungle-covered rocks of the hill of Patharghata, one of the 

 western outliers of the Raj mahal range, situated a little below Kalgaon, 

 on the Ganges ; and on the eminence of Sikrigali, another outlier of the 

 same range to the north-east. The specimens were met with under the 

 perpendicular and overhanging faces of low rocks, and under accumu- 

 lations of dead leaves. All those found were unfortunately destitute of 

 inhabitants, a circumstance the more to be regretted, as the conforma- 

 tion of the upper part of the peritsome and the presence of a wing, (a 

 character hitherto unknown to belong to land shells, as far as my in- 

 formation on the subject extends,) argue a corresponding variation in 

 the animal from any known type. The sinus probably affords a passage 

 to some process of the mantle, which the wing is intended to defend 

 from injury. 



The genus which most nearly approaches to Pterocyclos is Cyclosto- 

 ma, which is furnished with a circular aperture and a continuous peris- 

 tome ; but the characters above referred to will necessarily exclude this 

 shell from it. Lamarck's species, C. planorbula, which varies much 

 from his other species, and which is also widely umbilicated, appears 

 to have the greatest affinity to the shell before me ; and it has a still 

 closer affinity to it than would be supposed from Lamarck's de- 

 scription, if Wood's figure of Helix cornu-venatorium is to be relied on, 

 for the latter shell has a sinus (not alluded to by Lamarck) at the top 

 of the aperture ; but it shews no trace of the overhanging wing. La- 

 marck gives Helix cornu-venatorium of Gmelin as a synonyme of his C. 

 planorbula, but with a mark of doubt, and refers to a figure in Chem- 

 nitz, to which Wood also refers for his Helix cornu-venatorium. It is 

 probable, that that species will be found to be osculant between the 

 genera of Cyclostoma and Pterocyclos. 



If it had been my good fortune to have procured any of the Pferocycli 

 alive, I should have had a good opportunity of comparing the characters 

 of the animal with those of Cyclostoma ; having found several fine 

 specimens of a new species of the latter genus, with the live animals, at 



