REPORT ON THE GASTEROPODA. 311 



whole surface is frosted over with microscopic tubercles. Longitudinals — there are on the 

 last whorl 16 narrow, raised, dextrally convex, and rather oblique ribs; originating at 

 the angle of the whorls, where they are a little tubercled 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. 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 supra-sutural margination ; 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 improbably white when fresh. 

 Spire conical, subscalar in consequence of the prominence of the keel. Apex is small, 

 roundedly sharp, 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. Wlwrls 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 contract 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 angulated at the keel ; it is convex in its sweep to the edge of the canal, from 

 which it runs directly and obliquely to the rounded and open point of the pillar. In leav- 

 ing the body it retreats at once to the right to form the rounded sinus, which has an exces- 

 sively short upper side, but becomes large (though hardly deep) from the great forward 

 wing-like sweep of its lower margin, whose course is quite independent of the ribs ; 

 toward the edge of the canal this curve again retreats to the point of the shell. Inner 

 lip is a thin narrow glaze margined with a minute furrow ; it is oblique, but scarcely 

 convex across the body, direct on the short pillar, and cut off with a long slope to the 

 point of the canal, its edge being narrow, rounded, and scarcely at all twisted. H. 0'43 in. 

 B. 0'17. Penultimate whorl, height 0"07. Mouth, height 02, breadth 0'08. 



This species may be associated with the Plcurotoma nivalis, Lov^n, group ; for though very 

 unlike in texture of shell and length of mouth, yet the general form and style of ribbing are some- 

 what similar. 



