MOLLUSCA OF THE CHALLENGER EXPEDITION. 253 



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

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

 on tbe last wborl tbese become feeble, especially at tbe peri- 

 phery ; besides tbese there are sligbt, close-set, rounded stria? on 

 tbe 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 tbe lip, where the 

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

 tbere 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 lip 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 -wborl, it is thin and hollowed out, but below 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 tbe point of tbe 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 tbe low-lying and strongish spiral callus within. H. 0'67. 

 B. 06. Penultimate whorl, height 016. Mouth, height 0"505, 

 breadth 0-407. 



This species is very like tbe young of JSf. 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 



