558 THE VOYAGE OF H.M.S. CHALLENGER 



conical base. Suture : its position is distinctly defined by the sutural contraction, but the 

 suture itself is all but unrecognisable. Mouth small, a little oblique, oval, but pointed 

 above and below. Outer lip probably thickened in the full-grown shell, well arched. 

 Pillar rather long, a little oblique, with a patulous, thickened, and rounded edge, and 

 having a small contracted oblique canal in front of the point, which is cut off backwards. 

 Inner lip : pretty thick on the body, concave. H. 0"141 in. B. - 044. Mouth, height 0'04. 

 breadth 0-028. 



The three specimens of this species have all had the mouth broken ; in the one which is best 

 preserved the break has been repaired, but the restoration has not been fully completed, the labral 

 varix being absent. On the new part of the shell there are numerous very slight spiral threadlets, 

 not at all connected with the normal sculpture of the shell. From the thinness of the shell these 

 threads shine through, and are deceptively like teeth on the inside of the lip. 



22. Bktium leucocephalum, 1 n. sp. (PI. XXXVIII. fig. 7). 

 July 1875. Reef off Honolulu, Sandwich Islands. 



Shell. — Small, narrow, conical, brown-topped, white-tipped, rather feebly tubercled, 

 with three strongish spiral threads on the penultimate whorl, and a short square broad 

 sub-excavated base. Sculpture: Longitudinals — there are on each whorl about 12 coarse 

 rather ill-defined ribs, of which one or two on the latter whorls swell into poor varices ; 

 they do not appear on the first two regular whorls, and are absent on the base ; the 

 parting furrows are broad, shallow, and open. Spirals — there are on the earlier whorls 

 two, on the later three strongish threads, which rise into wide blunt tubercles in crossing 

 the ribs ; round the base of each whorl there is a minute threadlet, which entirely masks 

 the suture ; on the base this suprasutural threadlet is pretty strong, and lies just within 

 the periphery ; within this lies a little furrow with another thread on its inner side : the 

 centre of the base is a broad, slightly depressed furrow, within which is a small threadlet 

 defining the top of the pillar. Colour: the extreme tip is white, the next two whorls 

 chestnut, the following whorls white, the later ones pale ochry yellow. Spire rather high 

 and narrow, but with a tendency to broaden, conical. Apex consists of two small white 

 blunt subrounded whorls, of which the minute extreme tip is just visible. Whorls 8, 

 exclusive of those of the apex : they are short, broad, and of slow increase, with a sub- 

 conical and convex outline ; the body-whorl is short, and has a flatly rounded base. 

 Suture distinct, from the contraction of the whorls, but in itself invisible. Mouth small, 

 square. Outer lip convex. Pillar short, truncate, with a small oblique canal in front 



1 \ivxoxipa\o;, white-headed, so called from the colour of the apes. 



