CYCLOSTREMATID^. 15 



Genus VITRINELLA, C. B. Adams. 1850. 



Shell minute, depressed turbiniform, white, often with spiral 

 carinse, widely umbilicated, and the umbilical region widely indented, 

 whorls few, aperture large, rounded. Operculum unknown. 



V. VALVATOIDES, C. B. Ad. A considerable number of species 

 have been described by Prof. Adams from Jamaica and Panama. 

 They are mostly unfigured, and Dr. Fischer thinks that species of 

 Cyclostrema, Adeorbis, Teinostoma and Pseudorotella are included. 



Genus TEINOSTOMA, H. and A. Adams. 1853. 



Shell orbicular, depressed, polished or spirally striated, spire 

 short, obtuse, not projecting ; whorls few, the last with rounded or 

 angulated periphery ; umbilical region covered by a large, flat cal- 

 losity ; aperture transverse, distant from the axis, peristome con- 

 tinuous, lip sharp, simple. Philippines, Japan, Mazatlan. 



T. POLITUM, A. Ad. Deshayes enumerates fourteen species from 

 the Parisian Eocene. 



Section CALCEOLINA, A. Adams. 1863. 



Neritiform, depressed ; inner lip with a large wide callus, cover- 

 ing the umbilicus its margin straight, simple. T. PUSILLA, Adams. 



Japan. 

 Subgenus PSEUDOROTELLA, Fischer. 1857. 



Shell thin, diaphanous, subdiscoidal, paucispiral, finely striated ; 

 aperture oval, peristome not continuous, outer lip sharp ; umbilical 

 region covered by a polished, transparent callus. T. SEMISTRIATA, 

 d'Orb. West Indies. 



Parkeria, Gabb. 1880, Miocene of West Indies, is a synonym. 



Subgenus DISCOPSIS, Folin. 1869. 



Shell discoidal, much depressed, flattened above, carinated, vitre- 

 ous white, widely umbilicated ; whorls few ; aperture very oblique, 

 triangular, the margins united by a channeled callosity, prolonged 

 posteriorly. C. OMALOS, Folin. Gulf of Mexico. 



Subgenus LEUCORHYNCHIA, Crosse. 1867. 



Shell small, perforate, polished ; whorls few ; aperture rounded, 

 columellar and basel margins united into a callous rostrum, pro- 

 longed past the umbilical region, but without touching it ; peristome 

 continuous, simple. L. CALEDONICA, Crosse. New Caledonia. 



Evidently nearly allied to the preceding group. 



