Cyclostrema, Adeorbis, Vitrinella, and related genera. Ill 



smooth and shining and not at all pearly as understood in 3far- 

 garita, etc. The mouth cannot be said to be quadrangular ; the 

 peritreme is not continuous in the young, and even in the adult is 

 modified on the body-whorl into a vei*y thin glaze. The operculum 

 is very difficult to describe, as the whorls are not clearly defined. It 

 is circular, very thin, of a delicate horn-color, with central nucleus. 

 Around the center are two or three evenly separated circles (whether 

 spiral or not, 1 cannot determine), outside of these are irregularly 

 disposed wrinkles, with an occasional, very faint, more definite circle. 

 I encountered the same difficulty in studying the operculum of trilix 

 (even when mounted in balsam). Five whorls represented by circles 

 could be counted, but their spiral structure was impossible to trace. 



Fischer placed Circulus as a subgenus of his Solanderia^ 1880, of 

 the genus Gihhida Risso, 1826, among the Rhiphidoglossa. 



The relation of this genus to Vitrinella seems very close, and the 

 differences, although perfectly apparent when one has several species 

 from both to study, are difficult to define. It therefore seems best 

 to use Circidus simply as a section of Vitrinella for those species 

 which, like Duminyi, have the more sinuate eolumellar margin and 

 very wide umbilicus showing all the whorls. It should be redefined 

 as follows : 



Circulus Jeffreys, 1865 (sens, str.). 



Shell small, circular, depressed, not nacreous, of few more or less 

 convex whorls usually more or less grooved and carinated ; aperture 

 nearly circular, oblique, somewhat angulated below ; peritreme sim- 

 ple, more or less continuous, in the adult modified on the body-whorl 

 into a very thin glaze which is absent in the young ; umbilicus 

 wide, the reverse of the spire ; operculum thin, light horn-color, 

 with central nucleus, number of whorls doubtful (five or more ?) 



Episcynia Morcli, 1875. Type, E. inornata (d'Orbigny). Island of St Thomas. 



"Shell hyaline, the carina with a double series of cilia, apex sim- 

 ple, not inverted." Synopsis MoUuscorum Marinorum Indiarum 

 occidentalium, p. 155, mala. Blatter, xxii, 1875. 



Type, E. inornata (d'Orbigny). 



^ Solanderia Fischer, 1880 (non Duchassaing and Michelotti, 18 iG) = Rossiteria 

 Brazier, 1895 (type, Trochus nucleus Philippi). Proc. Linn. Sec. N. S. Wales, ix, 2d 

 series, p. 728, 1894-5. 



