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



flattening down of the extreme point of the first whorl, merely sufficient to prevent its 

 being prominent. Whorls 15 to 16, of very gradual and regular increase, rounded, but the 

 equal curve is slightly flattened for the first two-fifths of the whorl's height ; the base is 

 flatly rounded and rather produced. Suture linear, regular, impressed. Mouth rather 

 small, rhomboidal, having an acute angle above and at the point of the pillar, and an 

 obtuse angle at the corner of the base and at the top of the pillar. Outer lip very thin 

 and sharp ; it joins the body just at the circumbasal angulation, and springs at once very 

 much forward, so as to form with the body a small, shallow, but acute-angled sinus ; with 

 a slight and regular forward curve it thus advances to the angulation of the base, from 

 which it runs straight, flat, and slightly patulous to the point of the pillar, which it joins 

 at a bluntly-acute angle, forming a slight but not at all incised canal. Pillar is not at 

 all oblique, but is very slightly concave. Inner lip is entirely discontinuous across the 

 body, and first makes its appearance in a small and slight porcellanous pad, which 

 closely encircles the base of the pillar ; its sharp-edged, narrow, and slightly patulous face 

 forms the entire pillar. Umbilicus lies behind the thin pillar-lip, and is a distinct, little, 

 pervious, funnel-shaped pore, sharply defined by the intrabasal carination. H. 0'62 in. 

 B. 0-2. Penultimate whorl, height 0-083. Mouth, height 0-12, breadth 0"08S. 



I doubt very much whether this species really belongs to this genus. From Sars' Hcmiaclis it 

 seems, judging from his diagnosis and excellent drawings, to be distinguished by the thinness of the 

 spire and by the minuteness of the apes, the size of the umbilicus, and the smallness of the mouth ; 

 in doubt, therefore, I accept Dr Gwyn Jeffrey's advice, and classify it as an Aclis, a convenient, 

 because somewhat vague group. I have said that the shell is broadly subulate. The measurements 

 show very plainly that it is so only relatively to its fellows in the genus. 



2. Aclis hyalina, Watson (PI. XXXIV. fig. 2). 



Aclis hyalina, Watson, Prelim. Report, pt. 7, Journ. Linn. Soc. Lond., vol. xv. p. 246. 



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

 350 fathoms. Red mud. 



Shell. — Broadly subulate, high, conical, umbilicate, ribless or very faintly ribbed 

 on the earlier whorls, thin, glassy. Sculpture : Longitudinals — there are very many, 

 close-set, faint, irregular angulations of the surface, which, besides, is covered with 

 very fine hair - like striae ; these under a lens look very sharp and regular, but 

 under the microscope are seen to be rounded and irregular, made up of little incon- 

 stant curves, with changing swellings and depressions. Spirals— the surface is faintly 

 malleated in a somewhat orderly fashion ; but besides the larger system of malleations 

 there is a second system a good deal smaller and more irregular, and the raised edges of 

 these very slight depressions run in very numerous irregular and variable spiral lines, 

 which are so slight as only to be visible in a changing light. On the base the longi- 



