MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION". 441 



The specimen of this species from St. 56 has the spiral threads 

 very much finer than that from St. 24. The species has a strong su- 

 perficial likeness to P. emendata, Monterosato,=P. Renieri, Phil., 

 nee Scac. ; but that is a broader and larger shell, has a more tumid 

 body-whorl and a longer base ; its whorls are not so high-shoul- 

 dered, are more convex, are not so strongly keeled, are not so 

 deeply and strongly parted by the square impressed suture ; and 

 the apex is of the large blunt dome-type, consists of only two 

 whorls, and is simply carinated. 



40. Pletjrotoma (Kaphitoma) lithocolleta, n. sp. (\i0ok6\- 

 Arp-os, gemmed.) 



St. 23. March 15, 1873. Lat. 18° 24 r N., long. 63° 28' W. 

 Off Sombrero Island, St. Thomas, Dan. "W. Indies. 450 fms. 

 Globigerina-ooze. 



Shell. — High, narrow, conical, with a short base and a blunt 

 apex, bluntly angulated and tubercled, thin, smooth, ivory-white. 

 Sculpture. Longitudinals — there are none but very fine scratch- 

 like lines of growth ; behind and parallel to the lip-edge there 

 are three narrow sickle-shaped ribs, which are probably an 

 accidental feature. Spirals — very slightly above the middle of 

 the whorls runs a feeble angulation set with round but a little 

 narrowed and obliquely elongated knobs, of which there are about 

 12 on each whorl ; on the first regular whorl there are about 

 10 : before the end of the penultimate they have quite died out, 

 and even the angulation of the whorl tends to disappear. There 

 are faint traces of microscopic spirals over the whole shell, rather 

 in the texture than on the surface ; these are rather more distinct 

 below the suture ; and in the sinus-area there are two faint im- 

 pressed lines. Colour polished ivory-white. Spire high, narrow, 

 conical. Apex : the 2 j embryonic whorls are cylindrical, quite 

 smooth ; and these have the extreme point very much flattened 

 down on one side so as to make a perfectly rounded tip. Whorls 

 11 1 in all ; they are rather short, and of very regular increase, 

 slightly convex, but not contracted either above or below ; the 

 last is a very little tumid with a rounded base, contracting very 

 rapidly to a short broad snout, which is abruptly truncated at 

 the point. Suture rather oblique, fine, regular, defined by a slight 

 impression: it rises a very little at the mouth. Mouth pear- 

 shaped, small, narrow, little contracted in front. Outer lip some- 

 what thickened, with a small reverted edge in the sinus and at 



