MOLLTJSCA OF THE ' CHALLENGER ' EXPEDITION. 109 



of growth., "which, on the base, are curvedly radiating and strong. 

 Spirals — there is a spiral thread near the top of each whorl, con- 

 necting the upper series of tubercles, and the adjacent tubercles 

 at the lower ends of the ribs are confluent, forming a continuous 

 spiral ; round the edge of the base is a fine round carinal thread ; 

 of microscopic spirals there seems to be no trace. Colour trans- 

 lucent white. Spire high, narrow, and conical. Apex small, 

 glossy, roundly pointed and oblique, the extreme point rising 

 slightly on one side. The embryonic whorls are two, slightly 

 oblique, convex and perfectly smooth, but for some very faint 

 spiral scratches. After these faint and sparse riblets begin to 

 appear, and only'after two more whorls do these reach distinctness. 

 The second, though narrower, is higher than the third. Whorls 12, 

 of very gradual increase, flat on the sides, slightly carinated by the 

 projection of the lower thread of tubercles, a little contracted into 

 the suture, on the base scarcely convex but conical. Suture 

 linear and very minute. Mouth squarish, with a largish oblique 

 opening into the canal, which is semicircular, a little oblique, and 

 with very shortly reverted edge. Outer lip thin, straight, but 

 strongly angled at the corner of the base. Pillar very short, 

 perpendicular, rather broad, rather sharp-edged at the point, 

 where it is obliquely truncate and tilted to one side. Inner lip 

 a very thin layer of glaze. H. - 25. B. O065. Penultimate 

 whorl 0-03. Mouth, length 0-033, breadth 0027. 



While the general form of this species resembles C. nietula, 

 Lov., the sculpture is very distinct, and the apex, though blunt, 

 is much finer and sharper, and not inflated as in that species. 



9. Cerithium (Bittitjm) mamillanttm, n. sp. 



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

 nambuco. 675 fms. Mud. 



Shell. — In general aspect very much like O. nietula, Lov., but 

 narrower, and having a still blunter and more swollen apex. 

 Sculpture. Longitudinals — on the last whorl there are twenty-one 

 small, narrow, longitudinal ribs, which are curved so as to be pos- 

 teriorly convex ; they appear faintly on the outer circumference 

 of the base ; the line of these from whorl to whorl runs very 

 straight up the spire. The whorls are also microscopically striate 

 in the lines of growth. Spirals — near the suture a spiral thread 

 encircles the top of the whorls, and rises into minute tubercles 

 where it crosses the ribs ; near the foot of the whorls is a strong 



