M0LLT7SCA OF THE ' CHALLENGER ' EXPEDITION. 391 



slightly receding, while on the side it is first convex and then 

 concave to the point of the snout, where its course is very straight. 

 Inner lip a thin porcellanous glaze, spreads a little on the body, 

 from which the spirals are slightly cut away ; the lip is a little 

 concave above, then straight, and is early and obliquely cut away 

 on the front of the pillar, where it is slightly prominent, and finally 

 it runs out to the point of the snout as a thin edge bordering the 

 canal. H. 147. B. 04S. Penultimate whorl, height 0-24. 

 Mouth, total height 0*8, breadth 0*26. 



This species extremely resembles P. staminea ; nor should I be at 

 all surprised if, on a fuller series of specimens being obtained, the 

 two species should be ultimately united ; but the four specimens of 

 the former and the three of the present species obtained by the 

 1 Challenger ' are constant to one another and easily distinguish- 

 able. Besides distinctions which stand out in the description, the 

 form in P. trilix is slimmer, as if the whorls were more closely 

 twisted ; the snout is longer, finer, a little twisted, and is striated 

 to the point ; the shell is stronger, the pillar-edge of the front 

 canal where obliquely cut off is a little more contracted ; the 

 suture is much more deeply impressed, the apex is a very little 

 larger, and very slightly more pressed down on one side. The 

 sculpture, too, is crisper, sharper, and smaller in the spirals, so 

 as to produce a markedly different texture. In P. staminea, 

 where an inferior keel faintly appears, it lies much lower than in 

 P. trilix, in which it lies markedly above the suture. 



3. Pleurotoma (Surcula) lepta, n. sp. 



St. 157. March 3, 1874. Lat. 55° 55' S., long. 108° 35' E. 

 Southern Ocean, S.E. of Australia. 1950 fins. Diatom-ooze. 

 Bottom temperature 32°1. 



Shell. — High, fusiform, rather tumid, conical, with a produced 

 base and a very long fragile snout, thin, white, with very little 

 sculpture. Sculpture. Longitudinals — the whole surface is closely 

 scored with fine striae in the lines of growth ; of these, at irre- 

 gular intervals of about y^j inch apart or rather more, one rises 

 into greater strength and prominence as a rounded thread ; these 

 are stronger and more regular on the earlier whorls than on the 

 last. Spirals — two thirds down the whorls is a blunt angulation 

 bearing 4 or 5 fine, close-set, rounded threads ; on the last whorl 

 the angulation is obsolete, but its place is defined by the group of 

 close-set threads ; on the rounded shoulder above these are micro- 

 scopic striae and very indefinite rounded threads ; below the angula- 



