80 THE VOYAGE OF H.M.S. CHALLENGEE. 



and may, perhaps, coincide with other more important structural characters, which, 

 however, I have not been fortunate enough to discover. 



[PL XX. fig. 2, a—f. a Shell of female, seen from left side, h from above, c from 

 below, d from front, e male, seen from side, _/ from above. All magnified 40 diameters.] 



32. Cythere sahulosa, n. sp. (PI. XIX. fig. 1, a-h). 



Shell very tumid; its gTeatest height situated near the front, and equal to two- 

 thii'ds of the length ; the anterior extremity, seen from the side, is broad and very 

 obliquely rounded, the posterior narrowed, slightly produced below the middle, and 

 sloping steeply above; the dorsal margin is slightly gibbous in front, over the large 

 and conspicuous hinge-tubercle, and thence slopes with a gentle curve backwards ; ventral 

 margin straight, or slightly convex, and somewhat jagged or crenulated near the posterior 

 extremity ; seen from above, the outline is very broadly ovate, widest near the middle, 

 the lateral margins forming a bold curve from one extremity to the other; the anterior 

 extremity is obtusely pointed, the posterior broader and slightly produced ; end view 

 equilaterally triangular, the sides convex, apex emarginate. The surface of the shell is 

 thickly covered with angular depressions, the intervals between which are in many cases 

 rough, or almost spinous ; a wide longitudinal area in the middle of the dorsal and ventral 

 surfaces is, however, smooth, and free from sculptured ornament ; the hinge-line is deeply 

 depressed. Length, l-45th of an inch (-53 mm.). 



The specimen shown in figures e-fw, somewhat difi"erent in shape, and may perhaj)s 

 belong to the male ; while figures g-h have a less gritty surface, and show a peculiar 

 crenulation of the ventral margin ; a somewhat similar crenulation is visible on the upper 

 posterior angle in a and e, though not on the ventral margin. I do not imagine that 

 these variations, though interesting, are of any importance, except as showing a variable 

 development of the subspinous ornament of the shell. 



Cythere sahulosa occurred in moderate abundance in the dredging from Station 187, 

 ofi" Booby Island, depth 6 to 8 fathoms. 



[PI. XIX. fig. 1, a-li. a Shell of female seen from left side, h from above, c from 

 below, d from front, e sheU of male (?) seen from left side, / from above, g smooth variety, 

 shell seen from left side, h from above. All magnified 60 diameters.] 



33. Cythere cymha, G. S. Brady (PL XX. fig. 5, a-f). 



Oi/thtrc cijmha, Brady, Les Fonds de la Mer, torn. i. p. 157, pi. xvi. figs. 5-7. 



Shell of the female, seen from the side, higher in front than behind, greatest 

 height situated a little in front of the middle, and equal to two-thirds of the length ; 

 anterior extremity broad, fully rounded, and often finely denticulated from the front 

 of the ventral to the commencement of the dorsal margin ; posterior truncated, 



