MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION. 445 



pointed behind. Mantle paler. Siphon rather short. Head and 

 tentacles pale. JEyes large and black, on the upper outer side 

 and at about a fourth of the length of the tentacles, which are 

 rather solid, long, and cylindrical ; between these, and a little 

 above them, is the large prominent expanded snout, with a large 

 circular opening in front, round which the edge of the snout pro- 

 jects like a thick fleshy fringe. There are two unequal branchial 

 plumes. The radula consists of exceptionally minute, acicular, 

 sharp-pointed, horny prickles. There is no operculum. 



Shell. — Thin, horny, smooth, oval, with a tumid body-whorl, 

 a rather high, subscalar, small-pointed, round-whorled, shallow- 

 sutured conical spire, and a tumid lop-sided base, pointed at the 

 pillar, but with scarcely any snout. Sculpture. Longitudinals — 

 there are close-set fine hair-like lines of growth ; under the 

 microscope a system of much finer regular striae is seen to cover 

 the whole surface. Spirals — there are many fine, irregular, and 

 unequal rounded stria?, which faintly appear on the surface, but 

 are distinct on the pillar and front of the shell : besides these, 

 there are fine microscopic smooth scratches. Colour white, with 

 a faint tinge of yellow, horny, translucent, with a smooth and 

 shining, but hardly glossy, surface. Spire rather high, conical, sub- 

 scalar, from a slight bulge of the shoulder. Apex : 2% embryonic 

 whorls, subcylindrically conical, rising to a small, rounded, slightly 

 immersed tip, which is a little bent down on one side. Whorls 

 6 in all ; they are rounded, tumid, with a faint subangulation 

 below the sinus-area, in which there is a flattening rather than a 

 constriction of the surface ; below the periphery of each whorl 

 the form is cylindrical, with a very slight contraction into the 

 lower suture. The whorls increase regularly, but rapidly ; the 

 last is large and tumid, with a protracted rounded base cut off" 

 on the left by an oblique, scarcely concave line. There is scarcely 

 any snout, and the shell is truncated obliquely towards the point of 

 the pillar, which projects in a rectangular prominence. Suture 

 linear, impressed. Mouth very large, lop-sidedly oval, pointed 

 above and below. Outer lip a semicircular curve in both planes, 

 leaving a shallow, wide, shortly rounded sinus between the lip- 

 edge and the body. Inner lip : a thin, narrow pad stretches very 

 regularly along its whole length (which forms a very regular con- 

 cave curve) out to the thin, twisted, obliquely truncated edge of 

 the pillar : this edge runs out beyond the labial pad, and forms 



LINN. JOTJRN. — ZOOLOGY, VOL. XV. 34 



