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



body-whorl, a conical base, and a small, undefined snout. Sculpture : Longitudinals — 

 there are about 1 3 ribs on each whorl ; but they do not all exactly answer from whorl 

 to whorl ; they rise feebly just at the suture, but quickly increase in height, more slowly 

 in breadth ; in the sinus-area they are curved ; from the shoulder they are straight, with 

 only a slight curve on the base ; they die out on the snout ; they are narrow and rounded, 

 and are parted by rounded furrows of three times their breadth ; the whole surface is 

 also fretted with sharp minute lines of growth. Spirals — there is a straight, slightly 

 drooping shoulder below the suture ; this ends above the middle of the whorl in a distinct 

 angulation defined by a fine thread, which rises into small, sharp, rounded tubercles as it 

 crosses the ribs. On the penultimate whorl a finer thread begins to appear in the inferior 

 suture, but gradually rises above it ; it is from this lower spiral that the contraction of the 

 base begins : on the base are 3 or 4 finer spirals parted by spaces about four times their 

 width ; then follow several weaker crowded spirals, then one stronger and more pro- 

 minent : all these rise into small tubercles on crossing the ribs : beyond the end of the 

 ribs, on the snout, are some 6 fine distinct threads. The whole surface between these is 

 closely covered with very fine spiral threads, which on all the longitudinal lines of growth 

 are beset with most orderly and regular microscopic blunt prickles, which give the coral- 

 like aspect to the surface. Colour white ; the tip alone is smooth. Spire conical, scalar. 

 Apex consists of 4 embryonic whorls, which are bluntly conical, depressed, rounded, ribbed, 

 with a distinct suture, and rise to a minute tip (crushed). Whorls 8 in all, broad and 

 short, of regular increase, sharply keeled at the shoulder-spiral, and from this very slightly 

 contracted, but altogether angular, not curved : the last whorl is small, but attenuated, 

 not constricted, is scarcely convex on the base, and is produced into a short, vaguely 

 defined, and very obliquely pointed snout. Suture very slight, but defined by the angu- 

 lation at which the whorls meet. Mouth small, narrow, slightly pear-shaped, very little 

 oblique, bluntly triangular above, and prolonged into the short, open, scarcely narrowed 

 canal below. Outer lip flat at the shoulder, angulated at the keel, scarcely convex below 

 this ; the edge projects as a thin sharp lamina beyond the last longitudinal rib, which 

 serves as a varix from the point of the shell to the keel ; the edge is hardly convex, and 

 scarcely forms a shoulder above, the sinus being merely a small rounded hollow. Inner 

 lip : the glaze is exceptionally narrow and short ; the curve of the lip is a very little con- 

 cave at the base of the pillar, which is rather longer and narrower than one would expect, 

 and which is cut off in front with a long, slightly oblique, bluntly rounded, twisted edge. 

 H. 0-32 in. B. 0"13. Penultimate whorl, height 0'08. Mouth, height 016, breadth '06. 



This and Pleurotoma (Mangelia) acanthodes are extremely alike ; but one easily notices the relatively 

 shorter and broader form and the squarer outline and ribbing of this. Under that other I have men- 

 tioned a number of features of difference which, though individually minute, concur in marking the dis- 

 tinction of the two species. A comparison of this species with Pleurotoma (Rhaphitoma) nuperrima, 

 Tib. = Pleurotoma decussata, Phil, (not — Pleurotoma (Bhaphitoma) hispidula, Jan, which is certainly 



