MOLLUSCA OE THE ' CHALLElNTGER ' EXPEDITION. 393 



broadly rounded in front where the nucleus lies, pointed behind, 

 rather finely roundedly striate in the loop-lines of growth, which 

 are crowded, not on the pillar-edge, but on that lying toward the 

 outer lip of the shell. The body of the animal is a pale-buff 

 colour, but cannot be extracted without sacrificing the shell. 

 H. 1-6. B. 0-65. Penultimate whorl, height 0-27. Mouth, 

 height 0-1, breadth 0"43. 



This singularly beautiful species has some resemblance to P. 

 clara, v. Mart, (nee Reeve), from Patagonia, 60 fins., and is, like 

 that and those previously described here, eminently characteristic 

 of frigid waters. It wants the catenation of that species, has a 

 longer and more inflated body-whorl, with a smaller and shorter 

 apex, a more contracted suture, and stronger spiral threads. 

 4. Plettrotoma (Sttrcttla) rotundata, n. sp. 

 St. 246. July 2, 1875. Lat. 36° 10' N., long. 178° E. Mid 

 Pacific, E. of Japan. 2050 fms. Grrey ooze. Bottom tempe- 

 rature 35°-l. 



Shell. — High, narrow, fusiform, conical, with rounded whorls 

 and a shallow suture, below which the inferior whorl swells out 

 tumidly ; the last whorl is short and rounded, with a constricted 

 conical base and a long narrow snout. Sculpture. Longitudinals 

 — there are strongish, close-set, rounded, hair-like lines of growth, 

 specially strong below the suture. Spirals — over the whole sur- 

 face are strong, but unequal, rather distant, sharpish threads ; 

 those in the sutural area are, with two or three exceptions, weaker 

 • than those elsewhere ; about three at the periphery are somewhat 

 prominent. Colour porcelain- white under a thin yellow epidermis. 

 Suture fine, superficial, but well defined. Mouth is club-shaped, 

 being oval, with a long narrow canal below and a blunt angulation 

 above. Outer lip very evenly curved, but a little more steeply 

 above than below ; it is drawn out into a long straight line along 

 the side of the canal ; the edge-line, on leaving the body, retreats 

 very straight toward the left to the rather remote, wide, and 

 openly rounded, but very deep sinus, between which and the body- 

 whorl lies an acute triangular shelf, while below is the very high 

 shouldered and prominent lip. Inner lip is exceptionally narrow, 

 but strong and marginated ; it is very little concave at the junc- 

 tion of the body and the pillar, which is long, narrow, and is cut off 

 at the point with a long, little oblique, sharp, and scarcely twisted 

 edge. H. (?) 1-65. B. 0'6. Penultimate whorl, height 0-22. 

 Mouth, height 0-9, breadth 0*3. 



