RECENT BRITISH OSTRACODA. 



361 



ferous lobe, a subcorneal, simple, or obseurely articulate palp, which projects backward, 

 and terminates in three long setae, and a small branchial plate, bearing six radiating 

 respiratory setse. Postabdominal rami long and slender, bearing at the apex two long 

 and unequal curved claws, and a short seta ; a short seta springs also from the inner 

 margin of the ramus at or below the middle. The males furnished (mostly, if not 

 always) with two mucus-glands, consisting of a cylindrical axis, on which are set seven 

 whorls of radiating filaments, the whole connected with an efferent tube or "vas 

 deferens." 



The males of this genus are, except in a few instances, entirely unknown. Dr. Zenker 

 has, indeed, in his excellent memoir on the anatomy of the lower Crustacea, given 

 figures and descriptions of the males of three species ; but two of these belong to the 

 section comprised in the subgenus Cypria of that author, which may ultimately be found 

 to present generic characters distinct from Cypris proper. Eischer has also figured and 

 described the males of some few species. I have myself sought diligently for the males 

 of many of the commoner species of Cypris, but have only seen one example belonging 

 to C. ( Cypria) compressa, Baird. This is one of the species figured by Zenker. Mean- 

 time the peculiarities of the group Cypria seem scarcely sufficient to warrant its separa- 

 tion as a distinct genus. The "testis," or "mucus-gland," though hitherto seen only 

 in a few species, is doubtless present under some form in the males of all. And seeing 

 that it is, to all appearance, the secretory gland of the spermatic filaments, or " sperma- 

 tozoids," there seems no valid reason for applying to it any other name than that of 

 testis. 



The members of this genus inhabit exclusively fresh or slightly brackish water, and 

 are mostly natatory animals ; but a few of them, which have unusually short seta? 

 attached to the lower antennae, seem to be destitute of swimming-power, and constitute, 

 in fact, a link between Cypris and Candona. In external appearance, as well as in habit 

 of life, these approach the latter genus more closely than the former. To this category 

 belong C. reptans, serrata, and gibba. 



Though the structural diff'erences observed amongst the Cyprides are not of generic 

 importance, they are sufficient to form grounds of separation into several distinct sections 

 as follows : — 



a. Set^ of lower antennae plumose, subequal, reaching about as far as, or only slightly beyond, the apex 



of the terminal claws. 



* Second foot terminating in a short hooked claw, and one or more moderately long sette. 

 Second foot without a claw, ending in three setae. 



b. Setae of lower antennae non-plumose, very short, not reaching nearly to the apex of the terminal claws. 



c. Setae of lower antennae plumose, unequal; two or three exceedingly long, the rest short. Second foot 



ending in three unequal setae, one of which is exceedingly long. 



VOL. XXVI. 



