MOLLTJSCA OP THE ' CHALLENGER ' EXPEDITION". 247 



and the raised edges of these very slight depressions run in very 

 numerous irregular and variable spiral lines, which are so slight 

 as only to be visible in a changing light. On the base the longi- 

 tudinal striae are rather stronger, and the spiral system feebler 

 than on the spire. The edge of the base is rounded, but there is 

 a change of course at that part which produces a very slight an- 

 gulation. The lip of the small umbilicus is thickened and angu- 

 lated. Colour glossy on the surface ; the shell is milkily trans- 

 parent, glassy, and thin. Spire conical, with a very slightly 

 concave profile, long and fine. Apex small, rounded, but with a 

 very slight contraction and prominence on one side, in consequence 

 of the extreme tip being not entirely suppressed. Whorls 12, of 

 gradual and regular increase, convex ; the base is rounded, slightly 

 tumid, and produced. Suture linear, regular, rather sharply 

 though minutely impressed. Mouth small, oval. Outer lip leaves 

 the body a little below the contraction of the base ; from this 

 point it advances forwards so as to form with the body a small 

 but acute-angled sinus ; it sweeps round, not patulous, with a 

 very regular curve to the point of the pillar, which it joins at a 

 bluntly-acute angle, and forms there a slight but not at all incised 

 canal. Pillar is very slightly oblique and a little concave. Inner 

 lip is entirely discontinuous across the body, and first appears in 

 a minute thin abrupt edge, which surrounds the base of the pillar ; 

 its very thin, narrow, and slightly patulous face forms the entire 

 pillar. Umbilicus lies behind the thin pillar-lip, and is a minute 

 deep funnel-shaped pore, sharply defined by its angulated and 

 thickened basal lip. H. 0-42. B. 0-15. Penultimate whorl, height 

 0-062. Mouth, height 0-094, breadth 0'064. 



This species is very closely related to A. wiizon, ~W., and in any 

 classification they will certainly go together. Prom that species 

 this differs not only in the ribs, which are probably a very vari- 

 able feature, but, besides, the shell is proportionally broader, the 

 spire is less attenuated, the base is rounder and more tumid, the 

 suture is more linearly impressed and less open, the whorls are 

 more regularly rounded and of more rapid increase, the apex is 

 larger, and the extreme tip is more projecting. 



3. Aclis saeissa, n. sp. {sarissa, a pike.) 

 St. 122. Sept. 10, 1873. Lat. 9° 5' S., long. 34° 50' W. Off 

 Pernambuco. 350 fins. Mud. 



Shell. — Subulate, conical, smooth, white, glossy, with rounded 



