322 THE VOYAGE OF H.M.S. CHALLENGER 



run obliquely forward from right to left ; they sometimes extend to the base : besides 

 these, there are only slight hair-like lines of growth. Spirals — the prominence of the 

 tubercles forms an angulation at about one-third of the whorl's height above the suture ; 

 there are sometimes a few flatly rounded and feeble threads on the snout. The surface 

 is very delicately microscopically scratched. Colour ivory-white and highly polished. 

 Spire high, narrow, conical, with profile lines slightly interrupted by the projection of the 

 tubercles. Apex consists of 2^ embryonic whorls, which are small, globose, and flatly 

 rounded at the tip. Whorls 10, short, angulated, but only by the prominence of the 

 tubercles, which also gives the appearance of a sutural contraction ; the last is small, with 

 a rounded, very abruptly contracted, conical base, prolonged into a small, prominent snout, 

 which is almost imperceptibly bent backward. Suture linear, but well marked from the 

 profile-lines of the whorls above and below meeting at a slight angle. Mouth pear-shaped, 

 angulated above, and a little produced below. Outer lip very regularly curved, but 

 straight along the canal, a little contracted in the middle : on leaving the body it does 

 not immediately bend to the right, thus leaving a narrow but well-marked shelf along the 

 whole upper edge of the rather deep, narrow, rounded sinus, below which it advances into 

 a high-shouldered pinion : it scarcely retreats below this till close to the point of the snout. 

 Inner lip is very narrow ; it is scarcely convex on the body, and is somewhat angular at 

 the base of the conical pillar, down which it runs with a somewhat thickened, reverted, 

 and prominent edge defined by a small furrow ; it is scarcely cut off obliquely in front 

 with a narrow, thickened, rounded edge. H. 0'46 in. B. O'lG. Penultimate whorl, 

 height 0-07. Mouth, height 0'18, breadth 0"07. 



This species a good deal resembles Plcurotoma micans, Hds., but is a much narrower form, with 

 a higher and finer spire, more numerous whorls, and is not merely tubercled, but has its tubercles 

 prolonged into ribs. Than Plcurotoma pudica, Hds., it is longer, narrower, with a deeper suture, a 

 shorter canal, and a much blunter apex. Pleurotoma sigmoidca, Bronn, is broader, the whorls are 

 longer, the apex is blunter, the body-whorl is much longer, and that species has no open constriction 

 below the suture. 



52. Pleurotoma (Spirotropis) studeriana, v. Martens (PL XXV. fig. 7). 



Pleurotoma studeriana, v. Martens, Sitzungsbericht der Gesellsch. Naturforsch. Fr. Berlin, Feb. 1878, 



p. 22. 

 ,, ,, v. Martens, Conchologische Mittheilungen, vol i. p. 37, pi. viii. fig. 2. 



„ ,, Studer, Fauna Kerguelensland, Arehiv Naturgeschichte, 35th year, 1st vol. 



p. 136. 

 Drillia studeriana, Tryon, Manual, vol. vi. p. 209, pi. xiii. fig. 48. 



Station 149b. January 17, 1874. Lat. 49° 28' S., long. 70° 30' E. Kerguelen 

 Island, near entrance to Royal Sound. 25 to 30 fathoms. Volcanic mud. 



