MOLLT/SCA OF THE ' CHALLENGEE 5 EXPEDITION. 401 



over with microscopic tubercles. Longitudinals — there are on 

 the last whorl 16, narrow, raised, sinistrally convex, and rather 

 oblique ribs ; originating at the angle of the whorls, where they 

 are a little tuberculated and swollen, they are parted by furrows 

 of about the same breadth as themselves ; they die out across the 

 base, and do not appear on the snout. There are about 13 on 

 the penultimate whorl, and they diminish rapidly up the spire ; 

 the lines of growth are exceedingly faint and few, but sharp ; 

 they are most visible in the sinus-area and on the snout. Spirals 

 — the suture is marginated above by a minute thread, which lies 

 at the bottom of the superior whorl, and below by a somewhat 

 stronger thread, which lies at the top of the inferior whorl. The 

 sinus-area is bare. Slightly above the middle of the whorls 

 is the strong angulation, to which the prominence of the ribs 

 originating at this point gives great additional sharpness and dis- 

 tinctness. From this to the point of the shell the surface is 

 scored by rounded and prominent threads ; of these there are 

 three, pretty equal, on the earlier whorls, the third forming the 

 suprasutural marginatum ; a fourth appears on the penultimate 

 whorl, and 19 or 20 on the last, with one or two fainter ones 

 between ; the first two are feebler and closer set than the rest ; 

 on the body they are rather distant, on the front of the shell 

 rather stronger and close set. Colour -a pale buff, but not im- 

 probably white when fresh. Spire conical, subscalar in conse- 

 quence of the prominence of the keel. Apex is small, rounded, 

 consisting of 3-^ carinated, but otherwise perfectly smooth, whorls, 

 which form a short compact little cone, of which the extreme tip 

 is a little obliquely flattened down on one side. Whorls 10 in all ; 

 there is a drooping and very slightly concave shoulder below the 

 suture ; the greatest breadth is at the keel, below which the 

 whorls begin faintly, and with a very slightly convex profile, to con- 

 tract into the inferior suture ; the last contracts rather rapidly into 

 a short conical base, running out into a narrow, straight, somewhat 

 one-sided, and not very long snout. Suture invisible but for the 

 marginating threads above and below it. Mouth club-shaped, 

 being pointedly ovate above, and running out below into a well- 

 marked canal. Outer lip concave below the suture and angu- 

 lated at the keel ; it is convex in its sweep to the edge of the 

 canal, from which it runs direct and obliquely to the rounded and 

 open point of the pillar. In leaving the body it retreats at once 

 to the left to form the rounded sinus, which has an excessively short 



