REPORT ON THE OSTRACODA. 151 



[PI. XXXV. fig. 1, a-d. a Carapace seen from right side, h from above, c from 

 below, d from behind. Magnified 60 diameters]. 



Section MYODOCOPA. 

 Family I. Cypridinid/E, Baird. 



Shell mostly hard and compact in structure (sometimes thin and flexible), usually 

 smooth or finely punctate, but sometimes cavernous and strongly ribbed, notched at the 

 antero-inferior angle, so that when the valves are closed there remains a lai'ge aperture 

 for the protrusion of the antenna. Anterior antennae large, geniculated at the base, 

 many-jointed, and having several long ringed setae. Basal portion of the posterior 

 antennae broadly triangular, bearing a small secondary branch (different in the two 

 sexes), and a large natatory branch, which is mostly nine-jointed, and bears several long 

 ciliated setge. Mandibles rudimentary, the palp very large, geniculated, pediform, four- 

 jointed; first joint large and thick, bearing at the apex a slightly setose appendage like 

 a rudimentary branchial plate ; last joint very short and strongly clawed. Three pairs 

 of subpediform jaws, the first pair having four spinous lobes, of which the external is 

 largest and two-jointed, its first joint large, elongated, and subcjuadrangular, last very 

 short, and beset with numerous spines or claws ; second pair short and stout, composed 

 of several setose or unguiculate segments ; external segment short, three-lobed, beset 

 with short, finely-ciliated setae, and bearing at the base a very large semilinear branchial 

 plate, which is provided with numerous marginal setae ; third pair smaller, composed of 

 three spinous lobes, beneath which is a membranous subovate plate, bearing numerous 

 finely-ciliated setae. Feet, one pair only, forming a very long, flexuous, subcylincbical 

 annulose body, and armed towards the apex with long prickly spines. Postabdomen 

 large, composed of two broad closely adpressed lamina, and armed on the posterior 

 margin with a series of strong curved claws. Two compound pedunculated eyes, between 

 which is a large simple eye, and a short cylindrical tentacle. Male of less height than 

 the female ; eyes more developed ; copulative organs of complex structure ; ova and 

 embryos borne beneath the shell of the female. 



The Cypridinidae, owing to their considerable size and frequent capture in the surface- 

 net, have attracted more general attention from zoologists than any other division of the 

 Ostracoda ; but, compared with the Cypridae and Cytheridse, the number both of species 

 and individuals is very small. They appear to be most abundant in the warm surface- 

 waters of the tropical seas, contributing largely to the phosphorescence of those regions. 

 The males only (at any rate of those species which have been thoroughly examined) are 

 endowed with swimming power, the females being non-natatory, and passing their lives 

 wholly at the bottom, a condition imposed upon them by the absence of the tuft of long 



