MOLLTJSCA OF THE ' CHALLENGER ' EXPEDITION. 705 



part of it cat out bj tlie umbilicus ; they are flatteaed on the 

 contour and sliglitly scalar. Suture linear, but strongly defined 

 by the right-angled junction of the whorls. Mouth oblique, much 

 inclined to the axial line, rectangularly rounded, the pillar and 

 outer lip being parallel. Outer lip thin and broken, not descend- 

 ing. Pillar-lip shortly but flatly bent over the umbilicus, and 

 here it is patulous and sinuated, it then advances in a straight 

 line towards the base. It is toothed in the middle by a strongish 

 spiral protuberance, at which point it projects ; but from this 

 to the junction with the base it is thin and retreats. Umhilicus 

 very large, funnel-shaped, and pervious. H. 0"27. B. 0"3, least 

 0-25. Penultimate whorl 008. Mouth, height 0-1, breadth O'lS. 

 This very beautiful species is well defined by its exactly 

 conical form and very large umbilicus, which cuts the whole body 

 out of the inside of the last whorl, narrowing the base to an ex- 

 traordinary extent. The young shells are excessively like those 

 of Trochus (ZizipMnus) tiara, "VV., but are flatter, broader, and 

 more umbilicated. 



10. Teochus (Makgaiiita) clavatus, "W. (claviis, a nail.) 



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

 "West Indies. 390 fms. Mud. 8 specimens (none full-grown ?). 



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

 Pernambuco. 675 fms. Mud. 2 young specimens (?). 



Shell. — Small, conical, with a high spire and a tumid base, a 

 round mouth, and a deep umbilicus, and covered with sharp 

 prickles. Sculpture. Spirals — there are several small threads, 

 two of which, of equal strength and prominence, angulate the 

 whorls — one at the basal contraction, the other about halfway up 

 the Avhorl; on the base the}^ are somewhat closer set. The outer 

 lip does not meet the carinal thread, but the one below. Longi- 

 tudinals — the whole surface is crossed by close-set, slightly 

 oblique narrow laminge, which, in crossing the spirals, rise into 

 sharp vaulted prickles whose faces are turned towards the mouth. 

 Colour white, with a pearly lustre. Spire very high. Apex 

 minute, with the small embryonic 1| whorl rising from a minute 

 flat. Whorls Q\, angulated and narrow in the spire, but the last 

 inflated and expanded. Suture deeply impressed, somewhat de- 

 pressed, and very strongly defined. Mouth perpendicular, round, 

 slightly pointed on the base, and angulated at the upper carina. 

 Outer lip sharp, advancing far across the body towards thepillar- 



LINN. JOUBN. — ZOOLOGY, YOh. XIT. 53 



