Description of New Species of Marine Shells from the Coast of California. BY WM. M. GABB. The following are a few of the shells collected by Dr. J. G. Cooper, of the State Geological Survey, during his explorations along the coast of this State. The specimens are preserved in the collection of the Survey; most of them appear to be very rare in a living state, though I have encountered several of them in the later Tertiary deposits, especially in the Post Pliocene. MUREX, Linn. _S. G. Muricidea_, Swains. M. BARBARENSIS, G. M. t. unicolor, fusca; varicibus V-IX, haud magnis ad angulum auctis; varix ultima prælata; anfractu primo lævi, anfractibus V supra recte truncatis, infra parum convexis; tota superficie liris spiralibus et squamosis induta; apertura subelliptica, intus lactea; labio incrassato, polito; labro extante, tuberculis intus ornata; canali interdum recto, interdum recurvato. Long. ·77, lat. ·46, long. aper. ·2, long. canal ·24. 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. No. 1020, Mollusca, Survey Cabinet.