M0LLT7SCA OE THE ' CHALLENGER ' EXPEDITION. 395 



it sweeps out into a high and prominent shoulder. Inner lip little 

 concave at the junction of the body and pillar, which is straight 

 above, but towards the point is obliquely cut off" with a long, nar- 

 row, twisted edge, and bends a good deal to the left. H. - 9. 

 B. 0-38. Penultimate whorl, height 016. Mouth, height 0-51, 

 breadth 0-22. 



This is a stumpier form than P. leucotropis, Ad. & Eve., with a 

 more conical and less constricted base, and shorter and more bent 

 snout. From. P. oxytropis, while differing, of course, still more 

 markedly in most of these points, it differs yet more in sculpture. 

 Though a much smaller and narrower form and with a more 

 conical and less tumid base, it is in a general way very like P. cir- 

 cinata, Dali ; but that is destitute of the spiral sculpture on the 

 shoulder, which seems also to be the case with P. Kennicottii, 

 Dall, a smaller form than P. circinata, and which is also distin- 

 guished by a double keel on the last whorl. 



6. Pleurotoma (Surcula) plebeia, n. sp. 



St. 122. September 10, 1873. Lat. 9° 5' S., long. 34° 50' W. 

 Off Pernambuco. 350 fms. Mud. 



Shell. — High, narrow, fusiform, subscalar, angulated and 

 tubercled on the angle, strong, rough, yellowish white. Sculp- 

 ture. Longitudinals — the upper whorls are nearly bisected by a 

 bluntish angulation, which is made more marked by about 20 

 small, oblique, longitudinally elongated knobs, of which scarcely a 

 trace appears below or above the keel ; they become fewer up 

 the spire and die out on the last whorl ; there are very many, 

 rough, very unequal, curved lines of growth. The whole surface 

 is covered by coarse, unequal, and very irregular threads, varying 

 in their direction, and interrupted by the longitudinal lines of 

 growth ; these threads are most equal in the infrasutural tract, 

 where the line of the old sinus-markings lies ; below the keel they 

 occur alternatingly as stronger and finer ; on the base and snout 

 they are coarse, but almost disappear on the point ; they and the 

 suture are exceptionally independent of one another. Colour 

 yellowish porcellanous white. Spire high, narrow, conical, and 

 slopingly subscalar. Apex broken. Whorls probably 9-10, 

 rather narrow, somewhat hollowed on the shoulder below the 

 suture; below the keel their profile-line is straight, but contracted 

 to the suture below. The base (whose ujDper limit is defined by 

 a very slight angulation) is conical, drawn out pretty much in 



