MOLLUSCA. OF THE ' CHALLENGER ' EXPEDITION". 253 



crossed by numerous riblets, whose front edge is sharp ; they are 

 strongly convex in front, especially near the top of the whorl ; 

 on the last whorl these become feeble, especially at the peri- 

 phery ; besides these there are slight, close-set, rounded striae on 

 the lines of growth. Spirals — the whole surface is scored by faint 

 irregular and unequal furrows and microscopic lines ; there is a 

 twisted, prominent, but blunt umbilical carina. Colour por- 

 cellanous white under the yellow epidermis, with a broad buff 

 band which extends from the periphery halfway to the suture. 

 Epidermis yellow, thin, glossy, but roughened by longitudinal 

 folds. Spire short, but raised. Apex very small, prominent, but 

 the extreme tip scarcely rises into view. Whorls 6 (of which the 

 first three are embryonic and of a faint brownish purple), tumid, 

 well rounded, of rapid increase. Suture nearly horizontal, deep, 

 almost channelled. Mouth not much oblique, a little gibbously 

 semicircular, slightly more than three fourths of the whole height 

 of the shell, open, slightly and bluntly angulated at the point of 

 the pillar, pure white within, but with a slight ruddy tinge, 

 deepening to a rusty stain towards the edge of the lip, where the 

 buff spiral band lies. Outer lip a little contracted above, and 

 there faintly flattened ; it curves very equably throughout its 

 whole sweep ; it is open, but with a straight sharp edge, and 

 projects bluntly at the extreme point of the shell, where the um- 

 bilical carina joins it. Inner Up pure white, straight, oblique, 

 flat, and obsoletely channelled within, with a slightly thickened 

 rounded edge ; it is joined above to the outer lip by an expanded 

 but not very large nor thick callus ; below this, where it leaves 

 the body -whorl, it is thin and hollowed out, but below r the middle 

 of the umbilicus it is thickened by a prominent umbilical callus ; 

 below this it is slightly more reverted and thicker than above, 

 and it is very obtusely angulated towards the point of the pillar. 

 Umbilicus, which is defined by the basal carination, is deep ; in 

 consequence of the thinning and hollowing out in the inner lip 

 above and of a strong furrow between the umbilical callus and 

 the basal carina, it looks as if it were large, but it is contracted 

 by the low-lying and strongish spiral callus within. H. 067. 

 B. 6. Penultimate whorl, height 016. Mouth, height 0505, 

 breadth 0'407. 



This species is very like the young of N. rufa, Born, from Singa- 

 pore ; but it is higher in the spire ; the umbilical pad, which is white, 

 not brown as in that other, is also smaller, lower in position, and 



