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



53. Cythereprava (Baird), (PL XXII. fig. 4, a-f). 



Gythe)-eis prava, Baird, Proc. Zool. Soc. (1850), part xviii. p. 254 (Anuulosa), pi. 18, figs. 13-15. 

 Cyihereis deformis, idem, ibidem, pi. xviii. figs. 4-6. 



This, though much reaembling Cythere lactea, is a larger and more coarsely-sculptured 

 species, the sides of the valves show two or three flexuous, more or less prominent, 

 longitudinal ridges running along almost the entire length of the shell; the dorsal 

 margin is more irregularly broken, and the shell is wider in proportion to its length ; 

 the width and height are eqvial, and, in the female, exceed half the length. The end 

 view is irregularly quadrate, very broad dorsally. Length, l-38th of an inch ("66 mm.). 



Dredged at Nares' Harbour and other stations off the Admiralty Islands, in depths 

 of 16 to 25 fathoms. 



The types of this species, described by Dr Baird, were from the Mediterranean 

 (Tenedos), and my own collection contains a series of specimens from the same place. 

 The Challenger specimens here referred to are altogether coarser and clumsier in general 

 aspect ; the longitudinal ribbing is not so clean cut, nor is the pitted sculpturing of the 

 shell so well defined, and, seen dorsally, the outline is more obese and less attenuated 

 towards the extremities. But though the difi"erences are thus rather considerable, it 

 would not be easy to fix upon a line of separation, and I therefore prefer to consider 

 these specimens as local varieties of Dr Baird's species. 



[PI. XXII. fig. 4, a-f. a Shell of female seen from left side, h from above, c from 

 below, d from front, e male seen from left side, f from above. All magnified 60 

 diameters.]' 



54. Cythere cmivoUta, G. S. Brady (PI. XXII. fig. 3, a-d). 



Cythere convoluta, Brady, Ann. and Mag, jSTat. Hist. (1868), ser. 4, vol. ii. p. 182, pi xii. figs. 

 3, 4. 



Shell, seen from the side, subquadrangular, greatest height situated in front, and 

 equal to about two-thirds of the length ; anterior extremity smooth and broadly rounded, 

 posterior subtruncate and irregularly toothed, produced Ijelow and excavated above the 

 middle ; dorsal margin sloping from before backwards, abruptly and irregularly sinuous, 

 ventral slightly convex ; seen from above, the outline is irregularly ovate, widest in the 

 middle, with broad truncated extremities and irregularly jagged sides (the jags not 

 sufficiently marked in the plate) ; width equal to the height ; end view vaulted, base nearly 

 straight, sides boldly curved and deeply indented. The surface of the valves is marked 

 with numerous prominent, twisted, and sharply-cut longitudinal ribs, the intervals of 

 which are irregularly reticulated. Length, l-42d of an inch ("6 mm.). 



Dredged off Tongatabu, 18 fathoms (Station 172), and in 40 fathoms off the reefs at 

 Honolulu ; in both places amongst coral. The types were from Mauritius. 



