326 THE VOYAGE OF H.M.S. CHALLENGER. 



lip a rather depressed convex curve, a little concave at the top and flattened toward the 

 point : on leaving the body it retreats at once, forming a shallow, blunt V-shaped sinus, 

 from the lower side of which, with little of angulation, it advances very straight to the 

 edge of the canal, whence it slowly curves backward round the open point of the snout. 

 Inner lip spreads as a very narrow porcellanous glaze ; it runs very obliquely to the base 

 of the shortish narrow pillar, below which point it is a very little hollowed. The point of 

 the pillar is cut off with a very slight obliquity, and has a blunt and very slightly twisted 

 edge. Operculum small, oval, smooth, with hair-like stria?, apex terminal, colour pale 

 brownish yellow. H. 5 in. B. 0-23. Penultimate whorl, height O'l. Mouth, height 

 0'24, breadth 0-12. 



The blunt apex, the ribs, and coarse spirals of this species suggest some faint affinity with the 

 Pleurotoma nivalis, Loven, group ; but it is very remote. 



56. Pleurotoma (Spirotropis) stirophora, 1 Watson (PI. XXII. fig. 3). 



Pleurotoma (Drillia) stirophora, Watson, Prelim. Eeport, pt. 9, Journ. Linn. Soc. Lond., vol. xv. 



p. 422. 



Station 122. September 10, 1873. Lat. 9° 5' S., long. 34° 50' W. Off Pernam- 

 buco. 350 fathoms. Red mud. 



Shell.— High, narrow, angulated, obsoletely ribbed, tubercled, thin, polished, flinty 

 white, with an elongated conical base, longish pillar, and a blunt apex. Sculpture : Longi- 

 tudinals — the lower half of the whorls is crossed by obsolete, rounded, oblique, straight 

 ribs, with very slight rounded depressions between ; there are about 12, of increasing 

 indistinctness, on the last whorl, and 9 on the first regular whorl ; they take their origin 

 in a row of small, round, sharpish tubercles ; they do not extend to the base. The lines 

 of growth are faint sharpish scratches, and are quite independent of the ribs. Spirals — a 

 little above the middle each whorl is angulated and carinated, the carinal thread being set 

 with small, sharpish-pointed tubercles, in which the longitudinal ribs originate. The 

 sinus-area is smooth ; the rest of the surface is marked by very obsolete, depressed, rounded 

 threads. Colour greyish transparent white. Spire high, narrow, conical ; its profile-lines 

 but little interrupted by the broad, shallow, sutural depression which extends from keel to 

 keel of the successive whorls. Apex consists of nearly 2 embryonic whorls, which are 

 cylindrical, quite smooth, and end in a perfectly rounded tip, which is slightly immersed, 

 and scarcely, if at all, oblique. Whorls 7, short, and of slow increase ; they are angulated 

 above the middle, with a drooping, scarcely hollowed shoulder above, and a very slight 

 contraction of their straight line below ; the last is small, rapidly contracted on the conical 

 base, and running out into a somewhat one-sided, and slightly twisted, narrow, longish 



1 <rr»5o<£6jo£, keeled. 



