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



This singularly beautiful species has some resemblance to Phurotoma clara, v. Mart. («ec Reeve), 

 from Patagonia, 60 fathoms, and is, like that and those previously described here, eminently char- 

 acteristic of frigid waters. It wants the carination 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. 



18. Phurotoma (Surcula) rotundata, Watson (PL XXI. fig. 6). 



Pleurotoma (Surcula) rotundata, "Watson, Prelim. Report, pt. 8, Journ. Linn. Soc. Lond., vol. xv. 



p. 393. 



Station 246. July 2, 1875. Lat. 36° 10' N., long. 178° 0' E. Mid Pacific, east of 

 Japan. 2050 fathoms. Globigerina ooze. Bottom temperature 35"1°. 



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 surface 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 excep- 

 tionally narrow, but strong and marginated; it is very little concave at the junction 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 in. B. 0"6. Penultimate 

 whorl, height 0'22. Mouth, height 0-9, breadth 0'3. 



This is a species of interest, both from its habitat and from the simplicity of its rounded whorls 

 and of its sculpture. It exists unfortunately in the form of a mere fragment. It is a good deal 

 like Pleurotoma planetica, Edw., from the Eocene Bracklesham beds (see Eocene Moll., Palasont. 

 Soc, p. 212, pi. xxvi. fig. 3), but has not the flatly constricted band below the suture, which in that 

 species throws the whorls out in a high rounded shoulder. In Pleurotoma rostrata, Edw. (loc. cit., p. 

 218, pi. xxvi. fig. 8), though with less of a shoulder, there is a broader constricted belt, and there 

 are traces of longitudinal ribs. 



