238 



ON^ THE TOPOGRAPHY AXD GEOLOGY 



C. 1 11 r r i c u 1 u m . Gabb, n. s. 



Shell elongate, slender, spire bigli, whorls numerous, with their sides almost parallel, ornamented by a series of 

 elongate tubercles, laterally compressed and not so wide as the intervening s^iaces. These tubercles reach the 

 suture and are shouldered, producing a more or less marked superior angle to the whorl which however does not exist 

 in the interspaces. Crossing tlie whole surface is a series of small revolving lines. Canal moderately long, but 

 slightly twisted. Length about an inch. 



From the preceding' species, this can l^e distinguished by the ril^-like tubercle and 

 the entire want of convexity in the vdiorls, as well as by the peculiar "shouldered" 

 'appearance of the tubercle. 



C. Domini cense. Gabb, n. s. 



Shell robust, turreted, spire high, whorls numerous, the upper ones cancellated, the last two or three with a row 

 of large round tubercles on the angle and revolving lines, usually alternating in size. In some siiecimens, three or 

 four of the largest of these on the body whorl, are granular. Aperture small, canal moderately twisted. Length 

 about one inch. 



Distinguished by the cancellate upper whorls and the I'ouud tuljcrcles on the last 

 two or three volutions. One or two of my specimens retain traces of brown color 

 and look like bleached beach shells. 



C. plebium. Sby., Quart. Jour., Vol. VI., p. 51. 

 Id. Guppy, loc. cit.,. Vol. XXII., p. 290, pi. IG, fig. 9. 



A well-marked species, easily recognized by its straight ribs, usually alternating 

 with an ecpial number of thread-like ribs in the interspaces. I have a shorter and 

 broader form with the same sculpture which I consider a variety of the same species. 



? C. venustuni. Gabb, n. s. ' - 



Shell slender, very elongate, whorls numerous, flat on the sides ; suture linear, bordered both above and 

 below by a thread-like ridge surface bearing a few obscure, rounded varices and ornamented by obscure longitudi- 

 nal ribs crossed by about four revolving ribs making a small tubercle at each intersection. Between the latter ribs 

 are a few minute lines. Aperture unknown. Length nearly 1.5 inch. 



The shape of this shell is not unlike Turritella while its sculpture and the faint 

 varices seem to ally it to Cerithium. I have seen but a single specimen. 



C. simplex. Gabb, n. s. 



Shell broad, spire elevated, whorls eleven, rounded ; suture linear. Surface ornamented only by fine revolving 

 impressed lines. On some, especially of the upper whorls, faint traces of varices can lie detected. Aperture In-oad, 

 sub-oval, canal short, slightly twisted, inner lip not encrusted ; outer li}) simple, nearly straight. Length 1 inch, width 

 .5 inch. 



The round whorls, almost without ornament, and the naked inner lip and nearly 

 straight outer lip show this to be a decidedl}^ aberrant form in the genus, while its 

 columella and canal forbid a generic se]>aration. . : , , 



C. Yaquensis. Gabb, n. s. ■ , 



Shell minute, spire elevated, whorls numerous, rounded, bearing occasional rounded varices or irregular ribs ; 

 upper whorls most expanded on the lower side near the suture, narrowing gradually upwards. Surface marked by 

 a few large ribs extending from the suture to the base and crossed by fine i-cvolving lines. Canal short, curved, wide ; 

 outer lip internally striated. Length .85 inch, width .1 inch. . ^ , 



