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



almost obsolete, forming two small lobes or setse. Eyes mostly separate, sometimes 

 confluent, more rarely altogether wanting. Ovaries and testes not extending between 

 the valves. Male copulative organs very large and complex in structure. Mucus-gland 

 wanting. 



This family comprises by far the larger portion of the marine Ostracoda, but is very 

 sparingly represented in fresh water, of which, amongst the British species, only two 

 or three are inhabitants. Almost all the numerous fossil species are likewise refer- 

 able to the Cytheridse. The most important differences between this family and the 

 preceding are found in the structure of the lower antennse and the mandibular palp — 

 also in the number of feet, which in the Cypridse are two, in the Cytheridse three pairs, 

 the appendage forming the second pair of jaws in the former family assuming the shape 

 of an ambulatory foot in the latter. They are quite destitute of swimming-power. The 

 lower antenna is armed with a curved bi- or triarticulate seta, which reaches downwards 

 in front of the limb from the apex of the first joint, and mostly extends nearly to the 

 apex of the terminal claws : at its base this is connected by a duct with a gland or 

 vesicle situate in the anterior part of the body. It seems impossible to imagine any 

 other use for this organ than that of an urticating or poison-bearing weapon. In some 

 few species the lower antenna bears also near its apex a minute pyriform vesicle some- 

 what similar to that of Pontocypris &c., but considerably smaller. The limbs, especially 

 the antennae, are mostly strengthened on their anterior and posterior surfaces by bucklers 

 or plates of strong chitinous tissue, probably to afford a firmer attachment to their 

 powerful muscles. 



Genus 1. Cythere, Miiller. 



Valves unequal, mostly very thick and strong. Surface marked in the simpler forms 

 with slightly elevated papillse or tubercles, and fine punctations ; in others with deep 

 pits or fossae, and with very prominent elevations, which take the shape of sharp ridges, 

 spines, or tubercles. Lateral view subreniform or sub quadrangular, mostly highest in 

 front. The hinge-joint consists of two strong teeth on the right valve, which articulate 

 with corresponding depressions of the left valve ; the two teeth are often connected by a 

 strongly developed bar, which fits into a furrow of the opposite valve-margin; the 

 anterior tooth is much the strongest. The margin of the left valve mostly has a single 

 small tooth behind the anterior hinge-fossa, and sometimes one also at the posterior 

 extremity of the hinge-line ; the anterior fossa occasionally forms a complete circular 

 perforation of the marginal plate, and the central portion of the hinge-line is sometimes 

 minutely crenulated. Antennae robust ; superior five- to six-jointed, armed on the ante- 

 rior margin with three long curved spines, mostly one on the third and two on the 

 fourth joint ; lower four-jointed, the last joint short and stout. Mandibular palp three- 

 to four-jointed, bearing, in place of a branchial appendage, a tuft of two to five setae. 

 Eyes one or two. 



I have thought it necessary to include in this genus the forms assigned by Sars to the 

 two genera Cythere and Cythereis. In the first place, the characters taken by that author 

 as the ground of generic distinction seem to me inadequate ; secondly, four of our British 



