620 THE VOYAGE OF H.MS. CHALLENGER. 



slightly and linearly impressed suture, a largish somewhat obliquely set pear-shaped 

 mouth, with a straight conical base, which is not constricted, and has a very feeble swell- 

 ing in front. Sculpture : Longitudinals — the whorls are crossed by distinct, but rather 

 feeble rounded, straightish ribs, parted by shallow furrows of about their own breadth ; 

 they run on from whorl to whorl, and continue to the point of the base, where they bend 

 suddenly to the right ; of these, on the last whorl, there are about 15, the last forming a 

 strongish rounded varix on the back of the lip. Spirals — the whole surface is very finely 

 microscopically scratched, and the intervals of the ribs are microscopically scored with 

 fine rather distant threads, which become distinct on the base. Colour white. Spire not 

 very high nor narrow ; the profile-lines are slightly convex. Apex rather abruptly con- 

 tracted and small pointed, the small extreme tip rising a very little on one side ; it con- 

 sists of three conically globose whorls, which are microscopically ornamented with about 

 six spiral rows of minute white tubercles. Whorls 6 ; besides those of the embryo, the 

 earlier whorls increase very slowly, but the last three markedly, and are rather high and 

 somewhat convex, the base is rather short and obliquely conical. Suture slightly 

 impressed, and a little oblique. Mouth oval, oblique, prolonged into a gutter above, but 

 only a little angulated below. Outer lip thick, with a strongish varix, bevelled off to a 

 sharp nearly level edge ; it has a small sinus above, but almost none at all below ; it has 

 a pretty full curve throughout. Inner lip rather thin, with a slight thickening at the very 

 short pillar ; it is concave throughout, and at the tip of the pillar joins the outer lip with 

 rather a quick bend. H. 0-145 in. B. 0*048. Mouth, height 0'057, breadth 0'039. 



This species is superficially like Rissoina mercurialis, but is more oblique, the mouth being 

 larger and more thrown out to one side ; there is no constriction round the base, and the cord in 

 front is feebler; the apex in particular is much less attenuated, though the precise tip is more 

 pointed and the embryonic whorls more numerous. Other points of distinction may be noticed in 

 the description of the two species. 



11. Rissoina transenna, 1 n. sp. (PI. XLVI. fig. 10). 

 July 29, 1874. Levuka, Fiji. 12 fathoms. 



Shell. — High, narrow, conical, sharply finely reticulated, with a small protracted apex, 

 short whorls, a' broadly and squarely impressed suture, and a short rounded base, drawn 

 in by a furrow and a small sharp thread in front. Sculpture : Longitudinals — there are 

 about 12 to 14 fine sharpish remote ribs, which run down the spire continuously from 

 whorl to whorl to the point of the base, distinctly crossing the suture ; in direction slightly 

 oblique to the right ; the last forms a strongish varix on the lip-edge. Spirals — there are 

 on the penultimate whorl four, on the last there are six rather close-set rounded threads, 

 ■which form small tubercles in crossing the riblets ; the individual meshes of the network 



1 Thus called from the sculpture. 



