308 MANUAL OF THE MOLLUSCA. 
camerated within. Distribution, 18 species. South Europe; 
Corfu, India. 
Adamsiella (mirabilis) Pfeiffer, 1851 — Choanopoma, Pfr. 
(part) 1847. ‘‘ Operculum thin, rather cartilaginous.” Distribu- 
tion, 12 species. Jamaica, Demerara. Named after the late 
Professor C. B. Adams, of Amherst, Massachusetts. 
Cyclotopsis, Blanford. Asia. 
? FERuSSINA, Grateloup. 
Etymology, named in honour of Baron Ferussac. 
Type, EF. anastomeeformis, 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. 
CycLoPpHoRus, Montfort. 
Etymology, Cyclos, circle, phoreus, bearer. 
Type, OC. involutus, Pl. XII., Fig. 41. 
Shell depressed, openly 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. 
Distribution, about 150 species. India, Philippines, New 
Zealand, Pacific Islands, Tropical America. C. gibbus, Fer. 
(Alycaeus, Gray), has the last whorl distorted. C. 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. Pterocyclos (rupestris), Benson. Myxostoma and 
Steganostoma, Troschel. Shell 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 ? 
Cyclotus (fuscescens), Guilding (Aperostoma, Troschel). Shell 
depressed, widely umbilicated; operculum shelly, whorls 
numerous, with raised margins. Distribution, 44 species. West 
indies, Tropical America, India, Asiatic Islands. Fossil, Hocene, 
Isle of Wight. (F. Edwards). 
Leptopoma (perlucidum), Pfeiffer. Shell turbinated, peristome 
simple, reflected; operculum membranous. Distribution, 20 
