308 MANUAL OF THE MOLLUSCA. 



camerated witMn. Distrihidion, 18 species. Soutli Europe; 

 Corfu, India. 



Adamsiella (mirabilis) Pfeijffer, 1851 = Choanopoma, Pfr. 

 (part) 1847. " Operculum thin, rather cartilaginous." Distrihu- 

 tion, 12 species. Jamaica, Demerara. Named after the late 

 Professor C. B. Adams, of Amherst, Massachusetts. 



Cydotopsis, Blanford. Asia. 



? Ferussina, Grateloup. 



Etymology, named in honour of Baron Ferussac. 



Type, F. anastomaeformis, Gr. 



Synonym, Strophostoma, Desh. 



Shell rounded, depressed, umbilicated ; whorls transversely 

 striated above, spirally keeled below ; aperture turned obliquely 

 upwards, peristome simple. Operculum. ? 



Fossil, 5 species. Miocene — . Dax ; Turin. 



Cyclophorijs, Montfort. 



FAymology, Cydos, circle, phoreus, bearer. 



Ttjpe, C. involutus, PI. XII., Fig. 41. 



Shell depressed, o]3enly umbilicated ; aperture circular ; 

 peristome continuous, straight or expanded ; epidermis thick ; 

 operculum horny, many-whorled. 



Animal with long, slender pointed tentacles; foot broadly 

 expanded, not grooved. 



Distrihution, about 150 species. India, Philippines, New 

 Zealand, Pacific Islands, Tropical America. C. gibbus, Fer. 

 (Alycaeus, Grray), has the last whorl distorted. 0. cornu-vena- 

 torium, Sby. (Aulopoma, Troschel), Ceylon, has the peristome 

 free when adult ; the operculum is larger than the aperture, 

 and reflected over it. 



Sub-genera. Fterocydos (rupestris), Benson. Myxostoma and 

 Stoganostoma, Troschel. IShell depressed, nearly discoidal, 

 widely umbilicated ; peristome expanded, produced into a little 

 wing at the suture ; operculum sub -cartilaginous, spirally 

 lamellated. Distribution, 16 species. India, Ceylon, Birmah, 

 Borneo ? 



Cydotus (fuscescens), Guilding(Aperostoma, Troschel). Shell 

 depressed, widely umbilicated ; operculum shelly, whorln 

 numerous, with raised margins. Distribution, 44 species. West 

 Indies, Tropical America, India, Asiatic Islands. Fossil, Eocene, 

 Isle of Wight. (F. Edwards). 



Lcptopoma (perlucidum), Pfeiffer. Shell turbinated, peristoiue 

 einple, reflected; operculum membranous. Distributiorit 20 



