MOLLUSCA OF THE ' CHALLKNGER ' EXPEDITION. 



597 



slightly arched across the base, apparently nicked at the point 

 of the pillar. PilJar-Up 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 lar<::;ely to cover the umbilicus ; it then 

 advances straight and is toothed in front. Umbilicus small, 

 oblique-edged, with a crenulated margin. Height 013. Breadth 

 0-14, least 0-12. Penultimate whorl O'OS. Mouth, height 0-06, 

 breadth 05. 



Than JB. simplex, AV., this is a broader, smoother, less banded 

 shell. Than B. alta it is lower, less ornamented, with a much 

 smaller umbilicus. 



4. Basilissa alta, W. {alius.) 



St. 24. Mar. 25, 1873. Culebra Island, St. Thomas, Danish 

 W. Indies. 390 fms. Mud. 3 specimens, one full-grown. 



St. 120. Sept. 9, 1873. Lat. 8° 37' S., long. 34° 28' W. Off 

 Pernambuco. 675 fms. Mud. 1 young specimen. 



Var. oxTToMA, W. 

 Shell. — An equilateral cone, flat-based, sharply angulated. Small, 

 thin, delicately sculptured. Nacreous under a thin, white; calca- 

 reous surface. Sculpture. There are longitudinals about 45, hair- 

 like, strongly sinuated, flexuous, for they advance markedly on 

 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 whorls these longitudinals 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 stronger again above, the upper whorls presenting one in 

 particular, which connects the row of infrasutural beads. On 

 the base below the carina are four narrow and sharp spirals, 

 followed by about eight, which are broader and flattened, and 

 within there is one stronger than the rest, with about sixteen 

 rounded beads, which crenulate the edge of the umbilicus. The 

 furrows between these basal spirals are cut into little oblong pits 

 by the longitudinals. Colour a dead creamy white, with the 

 underlying nacre gleaming through. Spire high and conical. 



