MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION. 397 



Shell. — Long, narrow, biconically fusiform, sharply carinated 

 and tubercled on the keel, polished, thin, white. Sculpture. 

 Longitudinals — there are very many, fine, close-set, slightly raised 

 flexuous lines of growth. Spirals — there is a sharp keel which 

 lies abont ■§ down the whorls ; it is very prominent from the con- 

 cavity of the whorl above and below ; the sharpness of this keel is 

 due not so much to its crest, which is rounded, but to its beiug 

 beset by prominent round, couical, pointed tubercles, of which 

 there are about 15 on the penultimate whorl ; on the upper whorls 

 these are fewer, but they begin at once on the first whorl below the 

 embryonic shell ; on the last whorl they disappear entirely toward 

 the mouth. Besides the carina, there are many delicate lines • 

 three or four of these, very fine, smooth, and flat, come in below 

 the suture ; at about ^ inch below the suture is a fine, sharp, 

 engraved line ; about 6 more of these, but less strong, come iu 

 above the keel. Below the keel the sculpture is somewhat similar 

 but less distinct and less regular. On the snout the interstices 

 rise into rounded, slightly roughened threads, which on the extreme 

 point become feebler. Colour ivory-white. Spire high, narrow, 

 conical, but with the profile-lines broken by the deep concave 

 curves at the sutures. Apex, the 2-£ embryonic whorls are 

 small, cylindrical, and bluntly rounded at the top, which is 

 slightly pressed down on one side. Whorls lli strongly angu- 

 lated, with a concave curve between the keels ; they are rather 

 narrow and of very slow increase : the last one is a little tumid 

 with a very regular convex curve, which contracts evenly to 

 a long, projecting, narrow, cylindrical snout, lying very nearly 

 in the axis of the shell. Suture a very faint, delicate, and 

 regular line, well defined by the concavity of the whorl both 

 above and below it. Mouth club-shaped, but long and narrow, 

 sharply pointed above, and very much twisted in consequence 

 of the great depth and width of the sinus. Outer lip, origi- 

 nating markedly below the keel it leaves the body at a very 

 acute angle ; its edge, which is sharp throughout, retreats at 

 once, forming a very narrow and short ledge between the body- 

 whorl and the sinus, which is rounded and open, and whose depth 

 is due entirely to the great forward sweep of the lip below, where 

 it projects like the pinion of a wing and is slightly patulous ; it 

 curves in laterally to the origin of the canal, and then advances very 

 straight and scarcely patulous to the rounded point of the shell. 

 Inner lip is slightly cut out of the substance of the shell, is very 



LINN. JOUBN.— -ZOOLOGY, VOL. XV, 31 



