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



mouthed, oblique-edged, straight-sided, deep and contracted internally. Its edge is sharply 

 defined by a spiral thread, and is obliquely scored by the longitudinal ribs ; farther in its 

 walls are marked by hair-like lines of growth and faint spirals. Height 0'12 in. Breadth 

 0-14; least 0-11. Penultimate whorl, 0-23. Mouth, height 0"063, breadth 0-061. 



This species slightly resembles in sculpture the young of Margarita striata, Brod. ( = Trochus 

 cinereus, Couth., nee Da Costa), but in all details of form and ornamentation is very different. From 

 Trochus amabilis, Jeffr., besides the generic features, it differs in the depressed spire, in the absence 

 of the deep-cut suture, in the flatness of the base, and in all the features of minute, sculpture. From 

 Basilissa reticulata (Solarium), Phil., it differs in being much rounder on the base, blunter at the 

 edge of the umbilicus and at the carina, and in being much less delicately sculptured. 



7. Basilissa oxytropis? Watson (PI. VII. fig. 9). 



Basilissa oxytropis, Watson, Prelim. Eeport, pt. 4, Journ. Linn. Soc. Lond., vol. xiv. p. 693. 



Station 344. April 3, 1876. Lat. 7° 54' 20" S., long. 14° 28' 20" W. Ascension 

 Island. 420 fathoms. Volcanic sand. 



Shell. — Small, high, conical, scalar, with a sharp, expressed carina at the periphery and 

 a second carina above, angulating the whorls. Sculpture : There are a few close-set slight 

 spirals on the edge of the flat base ; there are many not close-set, flexuous, longitudinal 

 ribs above the periphery, but on the base merely lines of growth. These ribs in crossing 

 the upper carina form small sharp-pointed tubercles, of which there is also a trace on 

 the lower carina. The superior sinus lies just above the upper carina, the basal sinus 

 toward the middle of the base : both are well marked. The apex is small and flat, the 

 smooth embryonic 1^ whorl hardly rising at all. The whorls are of slow increase. The 

 pillar is perpendicular, with a strong rounded sinus, which corresponds to a swelling 

 within the umbilicus. The umbilicus is not large, but deep, funnel-shaped, with a puckered 

 sharp edge. In both specimens there are 5^ whorls to a height of 0'05 and a breadth 

 of 0-055. 



This species, which is not full grown, slightly resembles Basilissa alta, Wats., var. oxytoma, Wats., 

 but is more depressed ; the carina is sharper and is double, and the longitudinal ribs are very much 

 stronger. Than Basilissa costulata, Wats., this species is smaller, higher, more conical, and it is 

 scalar ; the whorls are more carinated above, and the peripheral carina is much more projecting ; the 

 apex is minuter and sharper, though the embryonic whorl is less raised ; the base is smooth but for 

 the marginal spirals ; the umbilicus is smaller. Compared to Basilissa reticulata (Solarium), Phil., it 

 has a less expressed carina, and the whorls are not angulated in the middle. 



o^iij, sharp ; reoxic, a keel. 



