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



there are fine close-set lines of growth. Spirals — on the last whorl a little below the 

 suture there is a bluntly angulated keel, on the top of which there is a slight rounded 

 thread ; between this keel and the suture the whorls are slightly excavated ; the upper 

 whorls are bisected by the keel ; on the base, rather within the middle of it and bordering 

 the umbilicus, is another slightly sharper keel, inside which is a broad shallow furrow with 

 one or two faint spiral threads in the bottom of it ; within this is a strong thread, followed 

 still farther within by another furrow- like the first, which is again bordered by a thread, and 

 within this the umbilicus becomes poriform. Colour dead white under a slightly mottled or 

 longitudinally banded smoky-brown membranaceous epidermis. Spire slightly raised and 

 scalar. Apex not very small, smooth, consisting of one whorl and a half; the extreme tip 

 is not prominent. Suture broadly and angularly impressed. Whorls 4 in all ; the last is 

 large. Mouth largish, a little oblique, suboval, slightly pointed above at the insertion of 

 the outer lip. Outer lip slightly patulous, thin, with a very slight thickening within the 

 mouth. Inner lip thickened at the upper corner, thin but not very short across the body. 

 Umbilicus strongly defined and marginated, with a broad open mouth rapidly contracting 

 to a pervious pore. H. 0-058 in. B. 0-078. Mouth, height 0-042, breadth 0-037. 



This species differs from Cydostrcma excavatum, Wats, (which it much resembles), in the form of 

 the shell and of the mouth, as also, and specially, in the form and sculpture of the umbilicus. 



3. Cyclostrema conicum, n. sp. (PI. VIII. fig. 9). 



Station 120. September 9, 1873. Lat. 8° 37' S., long. 34° 28' W. Off Pernambuco. 

 675 fathoms. Eed mud. 



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

 350 fathoms. Red mud. 



Shell. — Small, conical, subscalar, white, ribbed, and spiralled, with a raised spire, a small, 

 slightly raised, rounded apex, an impressed suture, a small round mouth and a poriform 

 umbilicus. Sculpture: Longitudinals — the last whorl is girt round with about 15 to 25 

 small, sharp, regular, equal, distant, lamelliform riblets, which run continuously from whorl 

 to whorl. Spirals — the whorls are faintly scored with very feeble threadlets and furrows ; 

 these vary considerably in sharpness and closeness. Colour white, not glossy. Spire 

 broadly conical, subscalar. Apex small, consisting of 1| smooth, turbinated whorls, with 

 the tip slightly raised. Whorls 4J, well rounded, short, small, all except the last, which is 

 tumid, with a short rounded base. Suture deeply impressed. Mouth small, round. Outer 

 lip thin, not expanded. Inner lip continuous, but very short and not disjointed on the 

 body, and having behind it a small funnel-shaped poriform umbilicus. H. - 06 in. 

 B. 0-055. Mouth, height 0-03, breadth 0-028. 



