Shell small, brown; whorl six, the first smooth, the remainder angulated, horizontally or a little concavely truncated above and very slightly convex below the angle; varices variable, from five to nine, usually about six or seven to a whorl, angular but not very prominent, except on the angle, where they are sometimes prolonged into long recurved processes, in other cases only making a prominent angular tubercle; the whole surface is covered with strong revolving ribs, crossed by fine squamose plates; aperture sub-elliptical, lips prominent, white within, the outer lip with five or six tubercles internally, last varix forming a broad lateral expansion to the lip; canal closed, straight, or more usually a little recurved.
Hab. Catalina Island, 40 fms., and Santa Barbara Channel, 20-30 fms. Dr. Cooper.
Nos. 515 b, c and d, Mollusca, Survey Cabinet.
PLEUROTOMA, Lam. 1799.
Turris, Bolt. 1798, not Turris, Hump, 1797.
S. Gen. Surcula, H. & A. Ad.
P. perversa, G.
P. t. sinistra, unicolor, rufo-brunnea; sub-fusiformis; anfractibus XI vel XII lævibus rotundato-compressis; apertura angusta, labio tenui, acuto.
Long. 1·2, lat. ·35, long. aper. ·45.
Shell sinistral, elongate sub-fusiform, apex acute, sometimes slightly bent, nuclear whorls two, very convex, loosely twisted and white; whorls, eleven or twelve, slightly convex; color a light reddish brown, somewhat lighter on the middle of the whorl; aperture narrow, canal short, inner lip moderately encrusted with a white callus, brown on the outer margin; columella twisted; outer lip acute, sinus rounded, shallow, broad and adjoining the suture.
Hab. Catalina Island, 60 fms., Dr. Cooper. Also fossil, not rare, in the P. Pliocene at San Pedro. One specimen from that locality is two inches long.