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



lij whorl slightly projecting. Wliorls 6, of regular and slow increase (but the specimen 

 is not full grown) ; in profile perfectly flat, the slope being scarcely broken by the supra- 

 sutural thread. Suture linear, almost invisible. Mouth perpendicular, irregularly rectan- 

 gular, broader than high. Outer lip sharp and thin, with a slight open sinus ; sharply 

 angled at the periphery, slightly arched across the base, apparently nicked at the point of 

 the pillar. Pillar-lip arched, strengthened by a thin pad, reverted on the umbilicus so as 

 to leave a groove behind it, with a slight tooth in front. From the body it bends very 

 much over to the left, so as largely to cover the umbilicus ; it then advances straight and 

 is toothed in front. Umbilicus small, oblique-edged, with a crenulated margin. Height 

 0'13 in. Breadth 014, least 0'12. Penultimate whorl, 0-03. Mouth, height 0-06, 

 breadth 0-05. 



Than Basilissa simplex, Wats., this is a broader, smoother, less banded shell. Than Basilissa alta, 

 Wats., it is lower, less ornamented, with a much smaller umbilicus. 



4. Basilissa alta, Watson (PI. VII. fig. 8). 



Basilissa alta, Watson, Prelim. Report, pt. 3, Journ. ;' Linn. Soc. Lond., 1878, vol. xiv. p. 597, 

 sp. 4. 

 „ Dall, "Blake" Moll., Bull. Mus. Comp. Zool. Camb., U.S.A., 1881, vol. is. p. 48. 



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

 Island, West Indies. 390 fathoms. Pteropod ooze. 



Var, Oxytoma, Watson (PL VII. fig. 8a). 



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

 675 fathoms. Eed mud. 



Habitat. — Gulf of Mexico. 



Shell. — An equilateral cone, flat -based, sharply angulated, small, thin, delicately 

 sculptured, nacreous under a thin, white, calcareous surface. Sculpture : There are 

 longitudinals about 45, hair-like, strongly sinuated, flexuous, for they advance markedly 

 at the periphery, where they are each ornamented by an elongated curved tubercle, and 

 on the base they again retreat so as to form a sinus. On the earlier wliorls these longi- 

 tudinals are much more distinct than on the later, and each starts from a little bead, which 

 lies close to the suture, but these beads are very feeble on the last whorl. In the intervals 

 of the longitudinals and parallel to them are very faint lines of growth. Of spirals there 

 are above the carina two stronger than the rest, with a sharp intermediate furrow ; above 

 these are several hair-like lines, which become feebler towards the middle of the whorl and 



