88 GENERA OF SHELLS. 



sub -channelled emargination. Columella flat- 

 tened, terminating at base in a point. 



The purpura is distinguished by the dilated aperture, 

 and the flattened and generally naked columella, ter- 

 minating in a point at the base, whose notch turns a 

 little upwards posteriorly. 



P. Persica, Rudolphi, patula, columellaris, succincta, con- 

 sul, armigera, bitubercularis, hippocastanum, undata, lia?ma&- 

 toma, mancinella, bufo, callosa, neritoides, planospira, 

 callifera, coronata, carinifera, scalariformis, sacellum, squa- 

 mosa, rugosa, textilosa, sertum, Francolinus, limbosa, ligata, 

 cruenta, lapillus, imbricata, lagenaria, cataracta, bicostalis, 

 plicata, fiscella, thiarella, rustica,semi-imbricata, echinulata, 

 hystrix, deltoidea, unifascialis, retusa, trochlea, clavus, 

 fasciolaris vexillum, bizonalis, nucleus. 



MONOCEROS. Shell oval. Aperture longi- 

 tudinal, terminating inferiorly by an oblique 

 sinus ; a conic tooth at the base of the lip 

 internally. 



The only distinguishing character between the mo- 

 noceros and purpura, is the projecting, horn shaped 

 conical tooth, on the right lip, which is constant in all 

 species. 



M. imbricatum, striatum, glabratum, crassilabrum. 



CONCHOLEPAS. Shell ovate, inflated, semi- 

 spiral ; summit inclined obliquely to the left 

 margin. Aperture ample, longitudinal, ob- 

 lique, with a slight emargination below. Two 

 teeth at the base of the lip. Operculum ob- 

 long, thin, horny. 



