546 THE VOYAGE OF H.M.S. CHALLENGER. 



and curvedly ribbed and furrowed longitudinally ; on the third the general sculpture of the 

 shell begins, but the highest spiral is absent, only its place is indicated by a broader infra- 

 sutural depression. The base has round its margin a sharp-edged thread, and close within 

 this a very faint furrow. Colour translucent glossy white. Spire is high, narrow, and has 

 straight outlines. The base of each whorl projects slightly beyond the top of that which 

 succeeds it, and the suture is sunk in a well-marked furrow. Apex is abrupt and rounded, 

 but the extreme point is obliquely prominent. Whorls 9, flat on the sides, narrowed 

 upwards, and constricted at the bottom above the suture. Suture linear and very minute, 

 but well marked by the furrow which lies above it. Mouth squarish. Outer lip incom- 

 plete. Pillar straight, short, and strong. Inner lip unformed. H. 0'147 in. B. - 0G. 

 Penultimate whorl, height 0'02. Mouth, length 0'03, breadth 0-028. 



The sculpture of this species is after the fashion of the Bittium rcticulatum (Da Costa), group, 

 but the form of the shell, its details of sculpture, and the shape of the apex are very distinct. It is 

 not quite full-grown, so that the form of the base is not entirely developed. 



10. Bittium philomelce, Watson (PI. XLI. fig. 2). 



Cerithium (Bittium) philomelce, Watson, Prelim. Report, pt 5, Journ. Linn. Soc. Lond., vol. xv. p. 113, 



sp. 13. 



Station 135c. October 17, 1873. Nightingale Island, Tristan da Cunha Islands. 

 100 to 150 fathoms. 



Shell. — Small, narrow, conical, blunt, outlines scarcely convex, rounded at the periphery 

 into the blunt square base, solid, dead white, not glossy. Sculpture : Longitudinals — on 

 the last whorl there are 21 rows of rather coarse round tubercles, parted by very narrow 

 furrows ; these lines run very straight up the spire. Spirals — on all but the first two 

 whorls there are three very equal spiral threads, which rise into tubercles as they cross the 

 longitudinals ; these threads do not appear on the first two whorls ; they are parted by 

 shallow furrows. The base of the whorls is sharply but shallowly contracted, and in the 

 bottom of the contraction, above the suture, lies a small spiral, which is undulated in 

 crossing the longitudinals, and which, on the base, forms a weak, feebly-tubercled circum- 

 ferential border. Spire is high, narrow, and has its outlines barely curved. Apex is 

 blunt and rounded, with a very minute oblique projection. Whorls 8, just barely convex 

 on the sides. Suture very minute and linear, but well marked by the furrow at the base 

 of the whorls. Mouth squarish. Outer lip broken. Pillar straight, short, and broad. 

 Inner lip a layer of glaze crossing the body and twining round the pillar. H. 0'128 in. 

 B. 0-05. Penultimate whorl, height 0'025. Mouth, height 0-03, breadth 0'02. 



This species, in its sculpture, belongs to the Bittium rcticulatum group. Than Bittium luscinice, 

 Wats., which it resembles, it is much smaller, more delicate in sculpture ; the apex is less squeezed 

 down than in that species. 



