RISSOIIDiE. 81 !► 



Subsection Parvisetia, Monts. 1884. 



Imperforate, spire rather short, apex obtuse, aperture expande(i, 

 semihinar, lip thickened. R. Scillje, Seguenza. 



Subgenus Rrssopsis, Garrett. 187?). 



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

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

 eolumella 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 w'ithin, outer lip margined exteriorly by a varix. 



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



Section Acinopsis, Monterosato. 1884. 



Aperture subcanaliculate anteriorily, 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. picta, A. Ad. 

 Section Alvtnia, Monts. 1884. 



Whorls shouldered, spiral sculpture stronger than the longitu- 

 dinal ribs. R. Weinkauffi, Schwartz. 



Galeodina, 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. 



Se(;tion Actonia, Monts. 1884. 



Lip inferiorly, obliquely expanded, externally thickene(l ; tnrbi- 

 nately elongated, decussed by close riblets and spiral stria". 



R. AHYSSK'oi.A. Forbes. 



Genus RISSOINA, d'Orbigny. 1840. 

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

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



