213 



Cerithlum — continued. 



petricolam. . turreted, smooth, with a thick border on the upper 

 part of the whirls, transversely grooved beneath — 1 inch. 

 spiratum. . round, turreted, smooth ; turns fiat and channelled 

 in the upper part ; base with one groove, plicated out- 

 wardly — 2 1 inches. 

 columnare. . subulate, transverse and vertical strise decussating, 

 with a marginal groove beneath the upper margin — 1 inch. 

 substriatum — conical, turreted, almost smooth ; the lower 

 whirls with simple distinct striae, the upper with obsoletely 

 crenulated ones — 1 inch, 

 quadrisulcatum. . subulate, turreted ; turns flat, with four grooves 



— f inch. 

 umbilicatum. . subulate ; whirls flat with four transverse grooves ; 



the columelUa umbilicated. . f inch. 

 pe7]f orat urn. . B\ihul3ite ; whirls rather convex, finely striated; 



columella perforated. . f inch. 

 clavosum. . smooth, turreted, with obsolete striae ; the lower 



whirls involving the upper. . ^ inch. 

 cancellatum. . subulate, turreted ; cancellated whirls convex ; 



columella subplicated. . small. 

 semigranosum. . turreted, decussated with subgranulated crossing 



striae ; canal very short. . ^ inch. 

 acicula. . subulate, smooth ; whirls subcarinated. . | inch. 

 iereh'ale. . turreted, smooth convex ; whirls with obsolete 



transverse striae. . small. 

 inversum. . turreted, subulate, left-turned; the whirls cancellated 

 by transverse keels and suboblique vertical striae. . f inch. 

 melanoides. . oval, turriculated, with transverse striae ; opening 



much like that of melania. . very small. 

 larva. . turreted, cylindrical ; w^hirls with two equal transverse 



granular keels. . very small. 

 gracile. . turreted and subulate ; whirls inversely imbricated. 

 incertum. . turreted ; whirls convex, with distant transverse 



striae and more numerous vertical ones. 

 emarginatum. . turreted, transversely sulcated, upper grooves 

 granulated, upper borders of the whirls subcanaliculated ; 

 the lip notched. . 2 inches. 

 rugosum. . turreted, upper whirls discussatedly granulated, the 

 lower slightly sulcated with one groove, lowest rugous 

 beneath. . Ij inch. 

 giganteum. . turreted, very long ; transversely striated ; whirls 

 nodose upwards ; columella with one plait ; opening ob- 

 long, oblique, with a canal which rather terminates back- 

 wards ; upper part of the right side with a lateral auriform 

 elongation. 

 nudum. . turreted ; whirls plicated in the upper part, numerous 



transverse striae ; no plait on the columella. . 3 inches. 

 unisulcatum. . turreted, numerous transverse striae, no plicae ; 



the turns have a single, nearly central groove. . f inch. 

 turritellatum. . turreted ; convex whirls with transverse unequal 

 striae ; a notch in the right border of the opening. . small. 



