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



contracted below in consequence of the dying out of the longitudinal ribs as they approach 

 the suture. The conical base contracts rather rapidly, and is prolonged into the straight, 

 very slightly reverted, direct, narrow, cylindrical snout. Suture a fine, regular, squarely 

 impressed line, whose course diverges a good deal from that of the spirals of sculpture. 

 Mouth club-shaped, being roundly oval and not angulated above, and with a long, narrow, 

 slightly twisted canal below. Outer lip sharp and thin, with a very regular curve from 

 the suture to the base of the snout, along the edge of which it runs sharp and straight to 

 the open, rounded, and thin point ; when it leaves the body, it retires at once to the left, 

 forming a deep, rounded, open sinus ; from this point its edge sweeps out in a full convex 

 curve, retreating slightly at the base of the snout, and then advancing straight to the point. 

 Inner lip porcellanous, longitudinally marked, narrow, straight, cut away obliquely to a 

 long fine point ; and then continued along the canal in a thin sharp edge, which toward 

 the point is slightly cut off backwards. H. 0"9 in. B. 0"32. Penultimate whorl, height 

 0-13. Mouth, total height 0*45, breadth 0'19. 



The narrow sharpish ribs of this species are suggestive of small buttresses, from which feature 

 the name is taken. The specimen is slightly chipped, and is, I think, not quite full-grown. It a 

 little resembles the young of Pleurotoma tenuis, Reeve, from China ; but the longitudinal ribs are 

 not nodulous. In form it slightly recalls Pleurotoma undatiruga, Bivoha, but in texture and all 

 details is utterly different. 



24. Pleurotoma (Surcula) bolbodes, 1 Watson (PI. XXII. fig. 6). 



Pleurotoma {Surcula) bolbodes, Watson, Prelim. Report, pt. 8, Journ. Linn. Soc. Lond., vol. xv. 



p. 402. 



Station 120. September 9, 1873. Lat. 8° 37' S., long. 34° 28' W. Off Pernambuco. 

 675 fathoms. Red mud. 



Shell. — High, narrow, conical, with a large bulbous apex, a contracted conical base, 

 and a long snout ; scarcely carinated, ribbed, with spiral threads, and an impressed suture ; 

 pale buff. Sculpture : Longitudinals — the whorls are crossed from suture to suture by 

 ribs, which are a little oblique and not curved ; they are narrow, pinched in laterally, and 

 most prominent a little above the middle of the whorls ; they do not extend to the base, 

 they are parted by shallow furrows rather wider than themselves ; on the last whorl there 

 are twelve, and they increase in number up the spire ; those at the top are a little sinuous 

 and crowded. The lines of growth are very faint, except on the base. Spirals — there 

 are about ten rounded prominent threads on each whorl, which stand out with special 

 prominence on the ribs ; on the last whorl these continue with very considerable 

 regularity and equality to the point of the shell ; in the constriction below the suture 



1 PoXfiMt);, from its bulbous apex. 



