422 MR. G. S. BRADY'S MONOGRAPH OF 



greatest height in the middle, and equal to considerably less than half the length, evenly 

 rounded in front, obliquely rounded behind, and obsoletely angular at tbe infero-poste- 

 rior angle. Superior margin evenly and gently arched, inferior nearly straight for the 

 anterior two-thirds, then gently convex, behind which it is slightly upturned. Outline, 

 as seen from above, subovate, sides nearly parallel, width equal to much less than half 

 the length ; anterior extremity obtusely pointed, posterior broadly rounded and emar- 

 ginate in the middle. End view nearly circular, keeled below. Shell smooth, orna- 

 mented with very small and distant circular papilla?, the ventral surface faintly grooved 

 in a longitudinal direction, these grooves sometimes extending obscurely round the 

 anterior margin. Colour light purplish brown; of specimens from shell-sand horny 

 yellow. Hinge formed by a median crest of the right valve and two terminal curved 

 flanges of the left valve ; altogether weakly developed, and showing no trace of crenu- 

 1 at ion, but an obscure tooth-like projection on the anterior flange of the left valve. 

 Penultimate joint of the upper antennae nearly twice as long ; second joint nearly four 

 times as long as the third; last joint half as long as the preceding ; basal joint very stout, 

 and bearing on its inferior margin a row of about twelve short spinous hairs. Terminal 

 claw of the third pair of feet long, slender, and flexuous ; a single short seta at the apex 

 of the penultimate joint, none on the antepenultimate. First pair of feet in the male 

 alike on both sides, subprehensile ; last joint bearing one strong, slightly curved terminal 

 claw, and one very short spine; second joint armed with one apical claw, similar in size 

 and shape to that of the last joint; second pair alike on both sides (?), basal joint bear- 

 ing a stout apical spine ; terminal claw long, setiform. 

 Length £g in. 



Hab. In deep water. Aberdeenshire coast (Mr. Dawson) ; the Minch and Channel Islands (Mr. J. G. Jef- 

 freys) j Devonshire coast (Mr. C. Spence Bate) ; Exmouth, Burrow Island, Isle of Portland, Swan- 

 sea, Tenby, Tobermory, Youghal (Rev. A. M. Norman) ; Pegwell Bay and Poole Bav (Prof. T. 



Mumbles, Frith of Forth, Thames 



(Mi 



W. C. 



tide-pools at Sunderland * (G. S. B.) 



miliamson, Esq. ; Tenby, T. Rupert Jones, Esq." (Dr. Baird) j off Ormeshead (Jfi 



Of C. elongata I have seen only one specimen containing the animal— a male. This 

 was found at the roots of Zaminaria at Tobermory by the Hev. A. M. Norman. In 

 some respects this differs rather remarkably from others of the genus, as, for instance, in 

 the conformation of the first and second feet, which are here alike on both sides. The 

 want of crenulation in the hinge-margins of the valves is also an important distinction ; 

 and notwithstanding the general resemblance of the species to the genus Cytheridea, I 

 cannot help suspecting that a fuller investigation of the structure of the animal may 

 show valid generic differences. 



Dr. Baird has doubtfully referred this species to Cytherina angmtata, Miinster; but 



mces m shape and in proportions of length and breadth appear to me too 

 serious to aUow of this identification. It approaches more closelv to « Bairdia " Mho- 

 domoides, Bosquet ; but is not precisely similar to it, as I have satisfied myself by the 

 examination ol specimens sent to me by that author. 



• This was in all probability a washed-up specimen, as the valves were empty. 



the differ 



