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



49. Cijthere bermudw, G. S. Brady (PL -XXL fig. 2, a-d). 



Gijthere serrulcda, Erady, Les Fonds de k Mer (1868), torn. i. p. 153, jjI. xviii. figs. 11, 12. 



Shell, seen from the side, somewhat siliquose, much higher iu front than behind, the 

 greatest height situated over the anterior hinge, and equal to at least half the length ; 

 anterior extremity broad and obliquely rounded ; posterior truncated, narrow, irregularly 

 emarginate and angulated about the middle ; dorsal margin sloping backwards with a 

 steep curve, and terminating in a produced angle ; ventral nearly straight, angulated at 

 the hinder end ; seen from above, the outline is that of a narrow parallelogram with two 

 broad produced extremities, the sides converging gently in front and almost at a right 

 angle behind ; width equal to rather more than one-third of the length ; end view 

 sub-pentagonal. Surface of the valves marked with three prominent longitudinal 

 ribs, the intei'spaces excavated into large irregular pits. Length, 1-5 0th of an inch 

 ('5 mm.). 



Specimens which seem fairly referable to this species, differing a little, however, 

 in shape as well as in the absence of serratures on the extremities of the valves, were 

 dredged in a depth of 435 fathoms ofl' Bermudas (Station 33). The type specimens 

 were from Colon-Aspinwall, but the specific name originally applied to them 

 (serridata) having been already used by M. Bosquet is here abandoned in favour of 

 hermudce. 



[PI. XXI. fig. 2, a-d. a Shell seen from left side, b from above, c from below, d from 

 front. Magnified 60 diameters.] 



50. Cythere cristatella, n. sp. (PL XIX. fig. 6, a-d). 



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

 height being equal to at least half the length ; anterior extremity moderately rounded and 

 slightly jagged ; posterior truncated, produced in the middle and angulated both above 

 and below ; dorsal margin elevated in front, sloping very gently backwards, and ending 

 in an angle at the hinder extremity ; ventral margin nearly straight ; seen from above, 

 the outline is compressed, much more than twdce as long as broad, subhexagonal, with 

 nearly parallel sides, which converge gradually towards the front, but very abruptly 

 behind ; the extremities form thick truncated prominences ; end view octagonal, widest 

 in the middle, the four oblique margins deeply sinuated. Surface of the shell irregularly 

 undulated, having an elevated longitudinal crest running parallel with the ventral 

 margin, and ending abruptly behind the middle ; the margins produced into a thick 

 encircling flange. Length, l-43d of an inch ("575 mm.). 



Dredged ofl" Booby Island (Station 187), 6 to 8 fathoms. 



[PL XIX. fig. 6, a-d. a Shell seen from left side, b from above, c from below, d from 

 front. Magnified 60 diameters.] 



