318 RISSOIID^E. 



Subgenus CINGULA, Fleming. 1828. 



Shell thin, smooth or spirally striated, spotted or banded near 

 the suture, outer lip sharp, or slightly thickened. 



R. CINGILLUS, Montg. 

 Oingilla, Monts. 1884, is a synonym. 



Section CINGULA (restricted.) 



Shell elongated, with subacute spire, whorls flatly convex. 



Section ONOBA, H. & A. Adams. 1854. 



Turbiniform or somewhat elongated, whorls convex, conspicu- 

 ously spirally striated, sometimes with short longitudinal plicae at 

 the suture ; aperture oval, peristome continuous, thin or slightly 

 thickened. R. STRIATA, Mtg. 



Section CERATIA, H. & A. Adams. 1854. 



Subcylindrical, thin, whorls flatly convex, with obtuse apex ; 

 outer lip thin and sharp. 



Animal with flattened, mostly short and claviform tentacles, foot 

 bifurcate behind. R. PROXIMA, Alder. 



Section HYALA, H. & A. Adams. 1854. 



Shell elevated conic, thin, hyaline, smooth or spirally striate ; 

 aperture oval, slightly emarginate anteriorily, outer lip thin, simple. 

 Operculum subspiral. 



Tentacles with setaceous summits. R. VITKEA, Forbes & Han- 

 ley. 



Section PLAGIOSTYLA, Fischer. 1872. 



Smooth, transparent, apex papillary, last whorl descending ; aper- 

 ture semilunar, pillar lip oblique, rectilinear, outer lip not varicose. 



R. ASTTTRIANA, Fischer. 

 Section SETIA, H. & A. Adams. 1854. 



Whorls few, smooth, ventricose, spotted, spire short, with obtuse 

 apex, aperture suborbicular. Animal with pilose tentacles. 



R. PULCHERRIMA, Jeffreys. 

 Subsection MICIIOSIOTIA, Monts. 18M. 



1m perforate or rimate, minute, brightly colored, often fasciate, 

 smooth. 



Pseudosetia, Monts. is a synonym. R. TURGIDA, Phil 



Subsection (!ix<;ruxA, Monts. 1884. 



Obtuse or globular, unieolored, lip thickened, covering the um- 

 bilicus. R, Ai;i)ioi;i, Jeffreys. 



