RISSOIID^E. 3U> 



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, 

 eolumella oblique, arched. R. TYPICA, Garrett. 



Subgenus AI.VANIA, Risso. 1826. 



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

 rounded, nodulously cancellated, aperture subcircular, crenulatecl 

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



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



Section Acixoi'sis, Monterosato. 1884. 



Aperture subcanaliculate antcriorily, columella tuberculate below 



R.CANCELLATA, DaCosta. 

 Section NEVILLIA, A. Adams. 18(i<s. 



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. 

 >Setion ALVINIA, Monts. 18*4. 



Whorls shouldered, spiral sculpture stronger titan the longitu- 

 dinal ribs. It. WEINKAUFFI, Schwart/.. 



Galeodina, Monts. 1884 (R. wrhmta, DaCosta), is a synonym. 



'Section THAPSIKLLA, 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. 



Bection ACTONIA, Monts. 1884. 



Lip inferiorly, obliquely expanded, externally thickened ; turbi- 

 nately elongated, decussed by dost' riblets and spiral strue. 



R. ABYSSLCOLA, Forbes. 



Genus RISSOINA, d'Orbigny. 1840. 



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

 ' luted; aperture semilunar, lip thickened within, a little reflected, 



