REPORT ON, THE GASTEROPODA. 591 



broad but low varix close to the lip-edge. Spirals — there are very faint microscopic 

 spiral markings. Colour translucent white, with a highly polished surface. Spire conical, 

 with continuous very slightly convex outlines. Apex quite smoothly rounded, without 

 any projecting tip or trace of break between the embryonic and adolescent shell. Whorls 

 5, quite flat and conical in their slope, without any angulation at the periphery ; the base 

 is very slightly convex. Suture linear, very slightly oblique. Mouth rather large, oval, 

 pointed above, and very slightly so at the front of the pillar, a little oblique. Outer lip 

 not patulous, except on the base, thin-edged, and with the edge bevelled in from the out- 

 side, in its arch semicircular. Inner lip rather thin, but defined on the body ; sharp, but 

 barely prominent down the pillar, with no umbilical chink behind it. H. - 088 in. 

 B. 005. Mouth, height 0'039, breadth 0'031. 



This species differs from Rissoa fayaleyisis, Wats., in size, sculpture, and form. 



9. Rissoa microstoma, n. sp. (PI. XLIV. fig. 10). 



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

 Island, West Indies. 390 fathoms. Pteropod ooze. 



Shell. — Strong, oblong, conical, translucent, glossy, strongly remotely ribbed, blunt, 

 round tipped, with barely convex-sided whorls, a linear suture, a squarish, flatly conical 

 base, and a small mouth. Sculpture : Longitudinals — there are on the last two whorls about 

 10 (on the earlier whorls 11 or 12) strong sharp-topped distant ribs, which run more or 

 less continuously, and somewhat obliquely, down the spire from whorl to whorl ; the 

 furrows between these ribs are wide and concave ; the lines of growth are microscopic 

 and very faint. Spirals — there are very faint microscopic markings. Colour translucent 

 white, glossy. Spire conical, with almost continuous lines. Apex large and rounded, 

 the extreme tip being unusually large and very inconspicuous ; the first two whorls are 

 quite smooth. Whorls 6, barely convex, very feebly and roundly angulated at the peri- 

 phery, which -is quite at the bottom of the shell, the base being barely convex. Suture 

 scarce appreciably impressed. Mouth small, roundly oval, very slightly pointed above 

 and at the point of the pillar, scarcely oblique. Outer lip patulous, except just at its 

 junction with the body, where it is slightly incurved, thin, bevelled off from the inside, 

 where a little remote from the lip-edge the opening is contracted by a varix. Inner lip 

 strong and defined on the body, thinnish sharp and slightly expanded on the pillar, and 

 though projecting there, there is scarcely the slightest furrow behind it. H. 0122 in. 

 B. 0-0G2. Mouth, height 0'039, breadth 0'035. 



This is a much narrower and longer form than Rissoa pernambucensis, with much stronger and 

 differently shaped ribs, and a smaller rounder mouth. 



