RECENT BRITISH OSTRACODA. 



385 



slender, divided into several curved teeth, and bearing near the apex a long ciliated 

 seta; palp robust, the basal joint large and bearing a branchial appendage, the last joint 

 very short and armed with several long spines. External segment of the first pair of 

 jaws very large, the rest very short and setose, bearing a branchial appendage. Second 

 pair of jaws destitute of a branchial appendage; palp large and subpediform, three- 

 jointed, last joint, in the female, armed with two long, slightly curved claws. Pirst pair 

 offset five-jointed, terminal claw very long. Second pair of feet flexuous, four-jointed, 

 last joint short, armed at the extremity with several stout setae, the margin of one of 

 which is conspicuously pectinated. Postabdominal rami well developed, bearing at the 

 apex two curved claws and a slender seta, inner margin bearing three long setse ; at the 

 base, close to the termination of the intestinal canal, is a long seta arising from a dilated 

 base. The ovaries are contained between the valves, forming a convolution or loop pos- 

 teriorly. "The testes extend round the whole circumference of the valves." Mucus- 

 gland apparently wanting. 



This genus is chiefly distinguished from the freshwater Cypridse by the excessive 

 development of the palp of the second jaw (which is distinctly three-jointed and pediform), 

 by the armature of the last pair of feet, and other minor peculiarities. In shell-struc- 

 ture it is very similar to Cypris, but in the conformation of the second jaw it shows an 

 approach to the Cytheridse. Sars observes that the animals are not very active in their 

 habits, though they are quite well able to swim, and are not, like Paracypris, compelled 

 to a mere crawling existence by the structure of their antennae. They appear, however, 

 to delight especially in a muddy bottom, and probably do not stir far away from it. I 

 have found them especially abundant amongst the mud of oyster-beds, and in very quiet 

 waters, where the bottom is covered with a great depth of soft ooze. The genus con- 

 tains at least three British species. 



1. PoNTOCTPnis MYTiLOiDES (Norman). (Plate XXV. figs. 26-30, Plate XXXVII. 

 fig. 4, and Plate XXXVTII. fig. 1.) 



Cythere mytiloides, Norman, Ann. & Mag. Nat. Hist. vol. ix. p. 50, pi. iii. figs, 1-3 (1863) . 



avena, Norman, Nat. Hist. Trans. Northumberland & Durham, vol. i. p. 17. 



Cypris serrulata, G. O. Sars, Zoologisk Reise i Sommeren 1862, p. 58 (1863). 

 Pontocypris serrulata, Sars, Oversigt af Norges marine Ostracoder, p. 15. 



British type. Distribution : Recent — Norway, Great Britain, Ireland. Fossil — Raised beaches and 

 glacial clays, Scotland and Ireland. 

 Carapace, as seen from the side, elongated triangular, broad in front, tapering to a 

 point behind ; greatest height situated at the anterior third, equal to considerably less 

 than half the length. Anterior margin broad and well rounded; posterior obtusely 

 pointed. Dorsal margin very high and almost gibbous near the front, sloping steeply 

 behind ; ventral slightly sinuated in the middle. Outline, as seen from above, lanceolate, 

 widest at the anterior third ; greatest width equal to one-third of the length, extremities 

 pointed. End view broadly oval. Surface of the shell granular or finely punctate, 

 thickly set with short appressed hairs ; colour purplish brown. The right valve is armed 

 at the infero-posterior angle with 8-10 short marginal teeth. Hinge-margins simple, 



VOL. XXVI. 3 G 



