MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION. 461 



intervals assume the form of slight rounded threads. Colour like 

 a shaving of ivory, from its thinness, gloss, and colour. The apex 

 is buff. Spire conical. Apex consists of 4 very small, conical, 

 scarcely convex, buff whorls, the upper part of which bears straight 

 little bars, and the lower part is minutely reticulated ; below the 

 buff-coloured surface the shell is porcellaneous. Whorls 9 in all, 

 slightly straight and sloping below the suture, convexly rounded 

 above, cylindrical below ; the last is a little tumid, with a 

 rounded base produced into a short, broad, lop-sided snout. 

 Suture very slight, as the inferior whorl laps up on the one above 

 it, but it is defined by the curve of the whorls. Mouth oval, 

 pointed above ; there is scarcely any canal below. Outer lip 

 very thin, a little contracted above, and patulous below ; its 

 curve is somewhat flattened about the periphery; its edge 

 forms a very regular curve with a slight shoulder above, be- 

 tween which and the body lies the broad, shallow, rounded sinus. 

 Inner lip is a thin narrow glaze which very soon dies out on 

 the oblique, twisted, fine edge of the short conical pillar, be- 

 yond whose point the front of the shell advances a good deal : 

 the junction of the pillar and the body is concave. H. 0*46. 

 B. 0-22. Penultimate whorl, height 0-11. Mouth, height 0-24, 

 breadth 0-11. 



This species slightly resembles Daphnella supercostata, E. Sm., 

 but is more obese, the mouth is shorter, the edge of the sinus is 

 not thickened, and the apex is sharp and sculptured, while in that 

 it is plain and blunt. It most resembles perhaps Pleurotoma 

 translucida, "Wats.; but that is smooth, and has a blunt rounded 

 apex. 



54. Plettkotoma (Deerancta) pudens, n. sp. 



St. 24. March 25, 1873. Lat. 18° 38' 30" ~N., long. 65° 5' 30" W. 

 North of Culebra Island, St. Thomas, Dan. W. Indies. 390 f ms. 

 Coral-mud. 



Shell. — Small, oblong, white, smooth, with a high, subscalar, 

 small and sharp-pointed apex, a short and scarcely swoln body- 

 whorl, and a conical base produced into a broadish, triangular, 

 lop-sided snout. Sculpture. Longitudinals — besides hair-like 

 lines of growth, there are some faint, very oblique, upwardly con- 

 vex folds, which are obsolete on the earlier and on the last whorls. 

 Spirals — the surface is covered with superficial rounded threads 



