REPORT ON THE GASTEROPODA. 287 



a sinuous double sweep, first convex and then concave, to the point of the snout, where 

 the edge is prominent, rounded, and patulous. Inner lip almost hyaline, being cut into 

 the substance of the body-whorl, but not extending beyond the mouth-edge ; it is slightly 

 concave above, straight in the middle, and very early and obliquely cut away in front 

 from which point, for the sixth of an inch, it advances to the extreme point of the shell 

 as a delicate, thin, sharp lamina bordering the canal. The operculum seems to have been 

 broken, probably in the attempt to extract it ; but it is obviously small, thin, and pale 

 yellow. H. 1-6 in. B. 0*51. Penultimate whorl, height 0*24. Mouth, total height, 0-83, 

 breadth 0'28. 



The animal of this species is preserved in one specimen, that from Station 146 ; it is deeply 

 retracted, and is of a pale buff colour. 



The name I have selected is descriptive of the sculpture of the shell. 



Surcula is not a satisfactory group in which to place this species, but the great length of its 

 canal excludes it from Spirotropis, which the general style of the shell suggests as its place. 



16. Pleurotoma (Surcula) trilix, Watson (PI. XXV. fig. 5). 



Pleurotoma {Surcula) trilix, Watson, Prelim. Report, pt. 8, Journ. Linn. Soc. Lond., vol. xv. p. 390. 



Station 150. February 2, 1874. Lat. 52° 4' S., long. 71° 22' E. Between Ker- 

 guelen and Heard Island. 150 fathoms. Coarse gravel. Bottom temperature 35°"2. 



Shell. — High, very narrow, biconically fusiform, subscalar, bicarinated, strong, white. 

 Sculpture : Longitudinals — there are very many unequal, strong, harsh, flexuous lines of 

 growth, of which one every here and there is stronger than the rest. Spirals — there are 

 two keels, of which the upper and stronger lies a little above the middle of the whorls, is 

 sharply pinched out, but has a rounded edge ; there is a drooping, but straight-lined 

 shoulder above, and the whorl is somewhat contracted below it, so that it has consider- 

 able prominence ; the lower keel is a rounded, rather prominent thread, which is the 

 more conspicuous from the contraction of the whorl below it into the suture ; between 

 these two keels, more or less in the middle, lies a thread more marked than any of 

 the others which, coarse, unequal, and interrupted, closely cover the whole surface ; of 

 these two or three in the line of the sinus on the shoulder, between the upper keel and 

 the suture, are somewhat stronger, more regular, and swollen than the rest ; while just 

 below this point, where the lines marking the lower edge of the sinus run, the surface is 

 almost free of spiral threads. Colour porcellanous white. Epidermis extremely thin, 

 smooth, pale yellowish. Spire high, narrow, subscalar. Apex consists of \\ embryonic 

 whorls, globose, smooth, and somewhat obliquely pressed down on one side at the extreme 

 tip. Whorls 1\, narrow, angulated, with a straight drooping shoulder below the suture, 

 slightly concave between the keels, contracted into the lower suture ; the base is conical, 



