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



and setiferoiis, and provided with a branchial phite. Second pair of maxillse without a 

 branchial plate ; palp large and subpediforni, three-jointed, last joint in the female, 

 armed with two long slightly curved claws. First pair of feet five-jointed, terminal 

 claw very long ; second pair flexuous, four-jointed, last joint short, armed at the extremity 

 with several stout setae, the margin of one of which is pectinated. Postabdominal rami 

 well developed, with three long marginal setse; at the apex two curved claws and one 

 slender seta ; also one long seta at the base, near the orifice of the intestinal canal. 

 According to G. 0. Sars, the ovaries are contained between the valves forming a loop 

 posteriorly, while the testes extend round the whole circumference of the valves. 



The palp of the second maxilla is here much more fully developed • than in the two 

 genera already described ; and the armature of the second pair of feet afi"ords another 

 good distinctive character. The animals, though quite able to swim, are far from active 

 in their habits, — in captivity at any rate being content chiefly to crawl on the bottom,- — 

 and, judging from structure, one would suppose that the habits of the genera Phlycteno- 

 johora and Aglaia must be pretty much the same. Paracypris, on the other hand, is 

 restricted entirely to a crawling life, by the absence of swimming setse on its lower 

 antennae. The specimens of Pontocypris, brought home by the Challenger, are remarkably 

 few, and those few present no very distinctive shell characters ; possibly they may be 

 immature examples. The reason of this paucity of specimens I believe to be that the 

 genus is essentially one belonging to shallow water, and no doubt littoral dredgings in 

 the warm seas of the tropical and sub-tropical zones would bring to light numerous new 

 species. Some few species from the Mediterranean and the Island of Mauritius I have 

 already had the oj)portunity of describing.^ In the open sea, and especially in shallow 

 sheltered inlets, round the British Islands, in depths of from 5 to 20, or 30 fathoms, 

 the two typical species, Pontocyiyris raytiloides, Norman, and Pontocypris trigonella, 

 Sars, are often very abundant. 



1. Pontocypris trigonella, G. 0. Sars (PL XV. fig. 4, a-d). 



Pontocypris trigonella, Sars, Oversigt af Norges marine Ostracoder, p. 16, 1865. 



Pontocypris trigonella, Brady, Monograph of Eecent Brit. Ostrac, p. 387, pi. xxv. figs. 31-34, 



and pi. xxviii. fig. 3. 

 Pontocypris trigonella, Brady, Crosskey, and Eobertson, Monog. Post-Tertiary Entom., p. 137, 



pi. xvi. figs. 26-28. 



Carapace compressed, oblong ; seen from the side subtriangular, greatest height 

 situated in the middle, and equal to half the length, anterior extremity moderately 

 broad and well-rounded, posterior rounded, but much narrower ; dorsal margin boldly 

 arched, highest in the middle, ventral very gently sinuated in the middle ; seen from 



' Ann. anil Mag. Nat. Hist., 1868 and 1869. 



