16 • CYCLOSTREMATID^. 



? Subgenus Microtheca, A. Adams. 1863. 



Shell globosely turbinate, widely umbilicated, somewhat porcel- 

 lanous, radiately, rugosely plicate, suture channeled and crenulated; 

 aperture semicircular, peritreme continuous, inner lip thickened 

 and arcuate, outer lip with thickened margin ; umbilicus crenulated. 

 Operculum unknown. C. crenellipeea, A. Ad. Japan. 



? Subgenus Morchia, A. Adams. 1860. 



Shell obliquely oval, depressed, widely umbilicated, convex 

 above, flattened beneath ; whorls rapidly increasing, the last di- 

 lated and ascending, embracing the others to the apex ; aperture 

 oblong, obliquely horizontal, dilated below, narrowed above, peri- 

 treme continuous, thickened, bilabiate. Oi^erculum unknown. (1 

 MoRELETi, Fischer, C. obvoluta, A. Ad. Japan, China, Red Sea. 



? Subgenus Cirsonella, Angas. 1877. 



Shell minute, globosely turbinated, smooth, narrowly umbilicated; 

 aperture circular, peristome continuous, slightly thickened. Oper- 

 culum unknown. C. australis, Angas. Australia. 



? Subgenus Haplocochlias, Carpenter. 1864. 



Shell solid, turbinate, subperforate ; aperture rounded, peristome 

 continuous, thick, exteriorly varicose, columella not callous. Oper- 

 culum unknown. C. cyclophoreus, Carp, Mazatlan. 



? Subgenus Cynisca, H. and A. Adams. 1854. 



Shell turbinate, depressed, with large, deep umbilicus encircled 

 by a spiral callosity ; whorls ornamented by spiral granular ribs ; 

 aperture circular, inner lip straight ; outer lip rather thick, sub- 

 crenulated, prolonged behind upon the penultimate whorl. Japan. 



C. granulata, a. Ad. 



