GASTEROPODA. 177 



C. cornu-venatorium, Sby. (Aulopoma, Troschel) Ceylon, has the peristome 

 free whea adult ; the operculum is larger than the aperture, and reflected 

 over it. 



Sub-genera. Pterocyclos (ru])estris), Benson. Myxostoma and Steganos- 

 toma, Troschel. Shell depressed, nearly discoidal, widely umbilicated ; pe- 

 ristome expanded, produced into a little wing at the suture ; operc. sub-carti- 

 laginous, spirally lamellated. Distr. 16 sp. India, Ceylon, Birmah, Borneo? 

 Cy dolus (fuscescens) Guilding (Aperostoma, Troschel). Shell depressed, 

 widely umbilicated ; operculum shelly, whirls numerous, with raised margins. 

 Distr. 44 sp. W. Indies, Tropical America, India, Asiatic Ids. Tossil. 

 Eocene, I. Wight (F. Edwards). 



Leptopoma (perlucidum) Pfr. <S'/i^// turbinated, peristome simple, reflected; 

 operc. membranous. Distr. 29 sp. Philippines, India, New Guinea, N. 

 Zealand, Pacific Ids. 



Megaloma^ (cylindracemn) Guild. (Earcimen, Troschel.) Shell oblong 

 or pupa-shaped, scarcely perforated, aperture circular ; operc. thin, horny, 

 many- whirled, flat. Distr. 19 sp. West Indies, Tropical America, Canaries, 

 India, Mauritius. Fossil. Eocene — . Paris and I. of Wight (£. i^or^^.?.) 



Craspedopoma (lucidum) Pfr. Shell turbinate, rimate, a little contracted 

 near the aperture ; operc. round, horny, many-whirled. Bistr. 3 sp. Ma- 

 deira, Palma. Fossil. Eocene — . I. Wight, Madeira. 



Cataulus (tortuosus) Pfr. Shell pupa-shaped, with the base keeled, pro- 

 ducing a channel in the front of the aperture; operc. cii'cular, horny, the 

 whirls easily separable. Distr. 6 sp. Ceylon. 



Diplommatina (foUiculus) Benson. (S/^^'/Z minute, (1 sp. sinistral) conical, 

 with costulated whirls ; peristome double ; operc. horny, multispiral. Distr. 

 3 sp. India. 



PupiNA, Vignard. 



Type, P. bicanaliculata, Sby. PI. XII. fig. 42. Australian Ids. 



Shell sub-cylindrical, usually polished; aperture circular, peristome 

 thickened, notched in front and at the suture ; operc. membranous, narrow- 

 whirled. P. grandis, Eorbes, has a dull epidermis. 



Distr. 8 sp. Philippines, New Guinea, New Ireland, Louisiades. 



Suh-gemis, TJiegostoma (nunezii) Hasselt. Aperture with a narrow 

 channel in the middle of the columeUar side. 6 sp. Philippines. Nicobar. In 

 U. lubricum (Callia, Gray) the sinus is obsolete. R. pupiniforme (Pupi- 

 nella, Gray) is perforated, and has a duU epidermis. 



Helicina, Lamarck. 

 Type, H. Neritella, Lam. 

 Sijn. OligjTa, Say. Pachytoma, Svv. Ampullina, Bl. Pitonillus, Montf. 



* Abridged from ^f e^rff^oTrea-siowa ; Swainson, who judiciously curtailed several 

 preposterously long names, allowed this to remain. 



