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



This is a shorter, broader shell than Bissoa amblia, with crisper, remoter ribs, and no umbilicus ; 

 the apex, too, though blunt, has the extreme tip smaller. 



7. Rissoa amblia, 1 n. sp. (PL XLIV. fig. 8). 



Station 85. July 19, 1883. Lat. 28° 42' N., long. 18° 6' W. Off Palma, Canaries. 

 1125 fathoms. Volcanic mud. 



Shell. — Thin, oblong, conical, glossy, horny white, closely ribbed, with rounded whorls, 

 a rounded slightly produced and minutely umbilicated base, a blunt rounded top, and an 

 impressed suture. Sculpture : Longitudinals — there are about 20 rounded wavy ribs 

 parted by rather narrower rounded furrows ; they become rather suddenly extinct on the 

 base. Spirals — there are very faint traces of flatly rounded spiral threads, of which three 

 round the outside of the base are stronger than the others ; the middle of the base is plain. 

 Colour translucent horny white. Spire conical. Apex very blunt and rounded, the 

 embryonic tip, consisting of a whorl and a half, being very large and depressedly globose ; 

 it is quite smooth, having only the most obsolete traces of very minute superficial rounded 

 longitudinal lines. Whorls 5|, convex, but subconical, with a very faintly angular bulge 

 round the bottom ; the base is rounded, but slightly flattened ; the whorls are of regular 

 increase, but the last is largish. Suture a little constricted, scarcely oblique. Mouth 

 rather large, not oblique, scarcely oval, with a very slight angulation above and at the 

 point of the pillar. Outer lip thin and sharp, semicircular, level on the edge. Inner lip 

 nearly semicircular, slightly detached just at the suture, thin, but defined and very short 

 on the body, on the pillar thin and sharp. Umbilicus small but distinct the edge of the 

 base being bluntly angulated, round, poriform, very slightly covered by the pillar lip, just 

 where it leaves the body. H. 0"093 in. B. 0-058. Mouth, height 0-039, breadth 0-03. 



This species is rounder in all its forms than either Bissoa pyrrhias, Wats., or Bissoa scanthias, 

 Wats. ; the sculpture is much less sharp, and there are no infrasutural tubercles on the ribs ; but 

 the apex in particular is entirely different. 



8. Rissoa pernambucensis, n. sp. (PL XLIV. fig. 9). 



Station 122. September 10, 1873. Lat. 9° 5' S, long. 34° 50' W. Off Pernambuco. 

 350 fathoms. Ued mud. 



Shell. — Strong, ovate, conical, white, feebly and remotely ribbed, blunt, round tipped, 

 with flat-sided whorls, a linear suture, a varixed lip, and a broad short base. Sculpture: 

 Longitudinals — there are near the mouth irregular hair-like flexuous lines of growth ; on 

 the last whorl there are from 15 to 20 narrow feeble rounded flexuous ribs, with broad 

 flat interstices ; these ribs barely appear on any of the earlier whorls ; the last forms a 



1 a,u|3XE~a, blunt. 



