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



to rather more than half the length ; anterior extremity obliquely rounded and usually more 

 or less beset with short spines ; posterior obliquely truncated, only slightly curved, more 

 or less spinous ; dorsal margin gently arcuated and irregularly indented, ventral convex 

 much longer than the dorsal margin owing to the obliquity of the extremities ; seen from 

 above the valves are widest behind the middle, thence tapering with a gentle curve 

 toward the front, abruptly backwards, and prominently angular at the widest point. The 

 surface of the shell is sculjrtured with deej), irregularly-shaped cavities of considerable 

 size. Length, l-30th of an inch ('8 mm.). 



A few detached valves only found in a dredging from lat. 52° 4' S., long. 71° 22' E., 

 150 fathoms (Station 150), and doubtfully at Station 296. These valves differ from the 

 type specimen in having a much rougher and more irregular style of sheU-sculpture, but 

 in general shape and character agree closely with it. The peculiarity of sculpture may 

 very probably depend on the age of the specimens. 



[PL XVII. fig. 3, a-cl. a, b Right valve seen from side, c from above, d from front. 

 Magnified 50 diameters. PL XX VI. fig. 4, a, h. These figures are doubtfully referred 

 to Cyihere normcmi.'] 



70. Cythere radula, n. sp. (PL XIX. fig. 4, a, b). 



Valves, seen laterally, oblong, quadrangular, higher in front than behind, the greatest 

 height equal to more than half the length ; anterior extremity well rounded, posterior 

 narrowed and obliquely truncated ; dorsal margin almost straight, but indented at 

 intervals, ventral convex ; the whole circumference, except on the dorsum, is broken 

 with strong, irregularly disposed spines of variable shape, but mostly short, acuminate, 

 and wide at the base ; seen from above the lateral margin is curved, widest behind the 

 middle, extremities obtusely rounded. The surface of the shell is very rough, covered 

 with a coarse net-work of ribbed sculpture, enclosing angular areolae, at the intersections 

 of which are occasional s]3ines or tubercles. Length, l-30th of an inch ('85 mm.). 



A single valve of this species was found in a dredging from off the Ki Islands, 580 

 fathoms. Station 191a. It is not unlike Bosquet's Cythere arachnoidea, but wants the 

 regularity of sculpture, and especially the longitudinal rib-work belonging to that 

 species. 



[PL XIX. fig. 4, a, b. a Left valve seen from side, b the same from above. Magnified 

 50 diameters.] 



71. Cythere dorsoserrata, n. sp. (PL XXIII. fig. 1, a-d). 



Shell compressed, oblong ; seen from the side, subovate, greatest height in front, and 

 equal to half the length ; anterior extremity broad, well rounded, posterior narrowed and 

 produced in the middle to a sharp point ; dorsal margin gently sloping backwards, and 

 finely serrated or dentated throughout the greater part of its course, ventral gently sinuated 



