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



whorl many (27 on penultimate, about 40 on the last whorl) fine, rounded, curved threads, 

 wLich correspond with the old lines of growth ; they are parted by minute furrows, which 

 are rather narrower than the threads. These longitudinals extend to the base, but not to 

 the snout. Spirals— the riblets are crossed by very similar spiral threads which form 

 minute knots at the crossings, and these are parted by little furrows which are rather 

 wider and less regular than the longitudinal ones, and have occasionally subsidiary thread- 

 lets in the middle : there are about 7 of these spirals on the penultimate and about 14 on 

 the last whorl : the sinus-area has very faint threadlets, about three in number, and the 

 first regular spiral below these is stronger than all the rest, and forms a slight keel ; they 

 cover the whole snout. Colour white. Spire high, conical, subscalar. Apex small, sharp, 

 consisting of three (probably, for the extreme tip is broken) embryonic whorls which have 

 the typical sculpture, the upper third being straight barred and the lower two-thirds 

 reticulately barred ; but the sculpture is very fine. Wliorls about 8 in all, of regular 

 but rapid increase ; in form convexly conical, slightly shouldered above : the last, which 

 is narrow, is produced into a convexly conical base and a broadish oblique-ended snout. 

 Suture is slightly impressed, and is somewhat strongly marked by the swelling of the 

 whorl immediately below. Mouth narrowly oblong, bluntly pointed above, where it runs 

 out into the small but rather deeply impressed and rounded gutter of the sinus ; below, it 

 is produced into a broadish canal. Outer lip regularly curved, but at the canal flattened ; 

 the edge forms a regularly curved sweep, prominent in the middle, and retreating into the 

 sinus and canal ; it is slightly contracted, sharp, crimped rather than toothed, thickened 

 a little way within ; in the sinus it is blunted and rounded into a gutter : an extension of 

 the outer lip surrounds the sinus and forms a small pad between that and the body-whorl. 

 Inner lip : there is a very thin glaze on the body and pillar : the edge of the pillar in 

 front has a very slight oblique bend, and is sharply rounded, but scarcely twisted. H. 031 

 in. B. 0-12. Penultimate whorl, height 0*07. Mouth, height 0-15, breadth 0"05. 



This markedly belongs to the same group as the preceding. It has the same Clathurclla apex 

 and much the same form as that, and is therefore also comparable with the species referred to on 

 the preceding page ; but it is obviously very distinct from them all 



3. Borsonia, Bellardi, 1839. 



Species. 

 1. Borsonia eeroplasta, Wats. 2. . Borsonia silicea, Wats. 



1. Borsonia eeroplasta, 1 Watson (PI. XVIII. fig. 2). 



Pleurotoma(Borsonia) eeroplasta, Watson, Prelim. Report, pt. 10, Journ. Linn. Soc. Lond., vol xv. p. 473. 



Station 24. March 25, 1873. Lat. 18° 38' 30" N., long. 65° 5' 30" W. North of 

 Culebra Island, West Indies. 390 fathoms. Pteropod ooze. 



1 xrigoTXatrbs, waxen. 



