CYCLOTUS. 275 



culum, C. Inoa, D'Orbiyny, fig. 1, a, 1, b. Shell, C. semi- 

 striatus, fig. 1, c. 



The majority of the species of Cy dolus proper are inha- 

 hitants of the East-Indian and Philippine Archipelagoes, 

 while a few are from New Guinea and the Fiji Islands. 

 The sub-genus Cyrtotoma is from Mexico ; the sub-genus 

 Aperostoma is geographically distributed into two groups, 

 one from South America, and the other from the West 

 Indies, especially from the Island of Jamaica ; not a single 

 species appears to inhabit the Old World. 



Species of Cyclotus. 



conoideus, Pfeiff. orbellus, Lam. 



corniculum, Mouss. planorbulus, Lam. 



diatretus, Gould. plebejus, Soiv. 



discoideus, Sow. pusillus, Sow. 



exiguus, Sow. Recluzianus, Pfeiff. 



filocinctus, Bens. scalaris, Pfeiff. 



Fortunei, Pfeiff. subdiscoideus, Sow. 



hebraicus, Less. substriatus, Sow. 



incomptus, Sow. variegatus, Swains. 



mucronatus, Soiv. volvuloides, Sow. 

 opaliuus, Mouss. 



Sub-gen. aperostoma, Troschel (Cyclopoma, Troseh.). 



Operculum with the margin of the whorls elevated into an 

 incurved lamina. 



Shell with the peritreme simple, continuous, acute. 



asperulus, Sow. distinctus, Sow. 



cingulatus, Soiv. dubiosus, C. B. Adams. 



corrugatus, Sow. Duffianus, C. B. Adams. 



crassus, C. B. Adams. giganteus, Gray. 



disjunctus, Moric. Inca, D'Orb. 



