318 RISSOIID^. 



Subgenus Cingula, Fleming. 1828. 



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

 the suture, outer lip sharp, or slightly thickened. 



R. ciNGTLLUS, Montg. 

 Oing'dla, Monts. 1884, is a synonym. , 



Section Cingula (restricted.) 



Shell elongated, with subacute spire, whorls flatly convex. 



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



Turbiniforni or somewhat elongated, whorls convex, conspicu- 

 ously spirally striated, sometimes with short longitudinal plicte at 

 the suture ; aperture oval, peristome continuous, thin oi' slightly 

 thickened. R. striata, Mtg. 



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



Subcylindrical, thin, whorls flatly convex, witli obtu.se apex; 

 outer lip thin and sharp. 



Animal with flattened, mo-^tly 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 lij) thin, simple. 

 Operculum subspiral. 



Tentacles with setaceous summits. R. vitrea, 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. AsTURiANA, Fischer. 

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



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

 apex, aperture suborbicular. Animal with pilose tentacles. 



R. pulcherrima, Jefl'reys. 

 Subsection Microsetia, Monts. 1884. 



lm})erforat(^ or rimate, minute, brightly colored, often fasciate, 

 smooth. 



Pseudosetia, Monts. is a synonym. R. TUR<ai)A, Phil 



Subsection Cingulina, Monts. 1884. 



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

 bili(!us. R. Alderi, Jefl'reys. 



