MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION. 4G3 



body-whorl and rounded base, produced into a square, prominent, 

 one-sided snout. Sculpture. Longitudinals — there are exceedingly 

 fine, faint, microscopic scratches in the line of growth ; at dis- 

 tances of about yo'S °f an i nc h apart these rise into small, 

 sharpish, round-topped riblets, which run continuously from the 

 suture to the snout, though on the base and below it they become 

 feebler ; on the earlier whorls these are of course less marked and 

 more close set : in the intervals of the larger riblets one or two 

 fainter ones occasionally appear. Spirals — below the slightly 

 concave sinus-area is an obtuse angulation, accentuated by the 

 slight prominence of the two small spiral threads which lie there ; 

 below this there are on the body-whorl above the lip-corner about 

 5 other small spirals not so prominent ; on the lower part of the 

 body and on the base they are weaker, but become stronger again 

 towards the point of the base and on the snout ; the intersection 

 of these with the spirals produces a slight spider-web-like appear- 

 ance*. Colour yellowish, without gloss ; the apex is buff. Spire 

 rather short and broad, scalar, and conical. Apex consists of 

 4-g- very small, conical, scalar, convex, buff whorls, parted by a deep 

 suture ; the first whorl and half is closely spirally striated with 

 about 10 minute threads : these threads, which are at first al- 

 most simple, are by degrees more and more fretted by longitudi- 

 nals, which break up the threads into minute tubercles : toward 

 the end of the second whorl longitudinal and oblique bars appear 

 somewhat vaguely and confusedly ; but presently the distinct 

 arrangement appears of short little bars above and a net- 

 work on the lower part of the whorls. Whorls *J\ in all, but the 

 shell is very likely hardly full-grown : they are almost horizontal 

 above, with a flat or faintly concave sinus-area, slightly angulated 

 at the shoulder, and below this cylindrical or a very little convex 

 to the lower suture ; the last is rather short, a little tumid, with 

 a long pillar-line on the left side, and a small square prominent 

 snout on the right. Suture very slight in consequence of the up- 

 lap of the whorls at their junction, but of course strongly marked 

 by the angulation of the line of junction. Mouth oblong, trian- 

 gularly pointed above, and ending in a very square broadish canal 

 below. Outer lip flatly arched, with a slight angulation below 

 the sinus-area and a marked pinch-in where it turns to form 



* From this the name is derived. 



