MOLLUSCA OE THE ' CHALLENGER ' EXPEDITION. 417 



tip of which is somewhat obliquely flattened down. Whorls 8 to 

 9, rather short, the last a little ventricose ; between the suture and 

 the angulation they are a little hollowed; below the angulation 

 the profile-line is convex with a slight contraction into the suture, 

 so that the breadth at the angulation and at the suture is equal. 

 The last whorl contracts rather rapidly on the slightly convex base 

 into a short conical snout, which on the right is so obliquely trun- 

 cated that it hardly projects, the curve of the lip passing on 

 almost without interruption to the point of the pillar. Suture 

 distinct, both from the curve of the whorls and from being itself a 

 little impressed. Mouth obliquely oval, pointed above, and with 

 a short broad canal below. Outer lip thin ; in the sinus it is 

 slightly thickened and very shortly reverted ; in its course it forms 

 a semicircular curve, a little contracted inwards in the middle, 

 but at the canal slightly patulous. It scarcely retreats in the 

 slightest degree at the sinus, which is round, open, shallow, and 

 close to the body ; below it the lip-edge advances straight (i, e. 

 with little forward curve), but w T ith considerable obliqueness, to 

 the edge of the base, from which point it curves backwards to 

 the canal, the edge of which is thin and patulous but not reverted. 

 Inner lip is thinly excavated in the substance of the shell, and is 

 very narrow ; concave above, it advances straight down the 

 shortish, conical, small, but strong-pointed pillar, which has a 

 narrow, but blunt, and scarcely twisted edge. Operculum small, 

 triangular, with a blunt terminal apex ; it is pale straw-coloured, 

 and is slightly corrugated with unequal furrows following the lines 

 of growth, some of which lines on the pillar-margin are slightly 

 laminated. H. 0*9. B. 036. Penultimate whorl, height 0-16. 

 Mouth, height 0*4, breadth 0-19. 



In general form this is like P. Studeriana, v. Mart., from Ker- 

 guelen ; but the breadth of the whorls lies at a much higher point 

 in each, the concave furrow below the suture is wanting in that 

 species, the ribs here are finer aud sharper, more crowded and 

 more oblique, and the apex is smaller and more cylindrically 

 prominent. P. patagonica, v. Mart., is also like ; but in that 

 the snout is much narrower and longer, the sinus is deeper and 

 more remote from the suture ; the ribs, which inform are similar, 

 are shorter, much less oblique, and die out on the penultimate 

 whorl ; and the whole surface is much more strongly cancel- 

 lated. In sculpture and form of sinus it is somew r hat like P. 

 fuegensis, E. Sin. In the specimen from St. 149 1>, which I attri- 



