31 tt 



Subsection PARVISETIA, Monts. 1884. 



Imperforate, spire rather short, apex obtuse, aperture expanded, 

 semilunar, lip thickened. R. SCILL.E, Seguenza. 



Subgenus RISSOPSIS, Garrett. 1873. 



Thin, elongated, cylindrical, apex truncate ; aperture subovate, 

 angular above, entire, peristome rather thin, somewhat expanded, 

 columella oblique, arched. R. TYPICA, Garrett. 



Subgenus ALVANIA, Risso. 1826. 



Shell oval, turbiniform, spire short, with sharp apex, whorls 

 rounded, nodulously cancellated, aperture subcircular, crenulated 

 or grooved within, outer lip margined exteriorly by a varix. 



Acinus, Monts, 1884, is a synonym. R. CIMEX, Linn. 



Section ACINOPSIS, Monterosato. 1884. 



Aperture subcanaliculate anteriority, columella tuberculate below* 



R.CANCELLATA, DaCosta. 

 Section NEVILLIA, A. Adams. 1868. 



Imperforate, acutely ovate, whorls convex, spirally lirate, longi- 

 tudinally striate ; columella callous, toothed below, outer lip smooth 

 or toothed within, varicose exteriorly. R. PICT A, A. Ad. 

 Section ALVINIA, Monts. 1884. 



Whorls shouldered, spiral sculpture stronger than the longitu- 

 dinal ribs. R. WEINKAUFFI, Schwartz. 



Oaleodina, Monts. 1884 (~R. carinata, DaCosta), is a synonym. 



Section THAPSIELLA, Fischer. 1884. 



Elongated conic, whorls flatly convex, cancellated by close, 

 small riblets and spiral lines, lip thin. R. RUDIS, Phil. 



It is Thapsia, Monts. 1884, not Albers. 1860. 



Section MASSOTIA, Bucq. Dautz. et Dollf., 1884. 



Shortly oval, last whorl swollen, aperture large, surface feebly 

 reticulated. R. LACTEA, Michaud. 



Section ACTONIA, Monts. 1884. 



Lip inferiorly, obliquely expanded, externally thickened ; turbi- 

 nately elongated, decussed by close riblets and spiral striae. 



R. ABYSSICOLA, Forbes. 



Genus RISSOINA, d'Orbigny. 1840. 



Rissoiform, ribbed or cancellated, whorls numerous, apex mamil- 

 lated ; aperture semilunar, lip thickened within, a little reflected, 



