MOLLUSCA. OF THE ' CHALLENGED ' EXPEDITION. 421 



Shell. — Rather short, fusiform, biconical, scalar, angulated, ob- 

 soletely ribbed, with rather strong spiral threads. The snout is 

 rather short, broadish, and lop-sided. Sculpture. Longitudi- 

 nals — there are on the last whorl about 18, very oblique, curved, 

 narrow, rather obsolete, irregularly arranged riblets parted by 

 wider shallow furrows ; they originate faintly at the suture, are 

 strongest and somewhat mucronate at the angulation, extend to 

 the lower suture, and appear on the base, but not on the snout ; 

 they are much stronger on the earlier whorls than on the last 

 one. There are very many fine hair-like lines of growth. Spirals 

 — there are a great many remote hair-like threads ; on the shoulder 

 below the suture these are fine and closer-set than on the body 

 and base ; the carinal one at the angulation and that next below 

 this, especially the first, are strong ; they are ornamented with 

 close-set, round, minute granules, which swell into small promi- 

 nent tubercles in crossing the riblets ; those on the carinal spiral 

 in particular are high, sharp, and horizontally elongated. In the 

 interstices of the ribs and spirals the whole surface is microscopi- 

 cally granulated : it is this granulated surface which gives the 

 peculiar crisp aspect to the texture of the shell, from which its 

 name is taken. Colour semitranspareut flinty, white, with a 

 crisp or slightly frosted aspect. Spire scalar, rather stumpily 

 conical, with its profile-lines much interrupted by the constric- 

 tion of the sutures. Apex : there are two globose embryonic whorls, 

 of which the first is immersed, but scarcely flattened down on one 

 side ; they are rather remotely microscopically regularly striated. 

 Whorls z>\ in all ; they are short, broad, of slow increase, with a 

 rather long sloping shoulder and a sharp carinated angle, below 

 which they are cylindrical, with a very slight contraction to the 

 suture ; the last is broadest at the keel, and from this point con- 

 vexly contracted to the rather short, broadish, conical snout. 

 Suture linear, but well marked by the contraction of the whorls. 

 Mouth rather large, rhomboidally pear-shaped, with three angles 

 above, and. prolonged below into a wide open canal. Outer lip 

 thin, angulated, rectilinear above to the keel, flatly curved 

 below ; on leaving the body it at once retreats to the left, form- 

 ing in the shoulder a shallow, open, rounded sinus ; below the 

 angle it advances very little ; and at the snout its retreat is small. 

 Inner lip : there is a thin narrow glaze on the body and pillar ; 

 at the base of the pillar is a slight rounded angle : the pillar is 

 short, conical, and straight ; its point is very slightly truncate, 



