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



extending between the valves. Male copulative organs very large and complex in 

 structure. Mucus gland wanting. 



This family, which includes by far the greater number of the marine Ostracoda, differs 

 chiefly from the Cy^ridse in the structure of the posterior antennae and mandible-palp, 

 and in having three instead of two pairs of feet, the appendage forming the second pair 

 of jaws in the Cypridse assuming the shape of an ambulatory foot in the Cytheridae. They 

 do not swim, but the posterior antenna is armed wdth a curved tubular seta, connected 

 with wdiat appears to be a poison gland, situated near the base of the limb. The limbs, 

 both in this family, and in the Cypridse, are often strengthened on their anterior and 

 posterior surfaces, with dense chitinous plates, which give firm points of attachment 

 to the powerful muscles of the interior of the limb. 



Cythere, Miiller. 



Cythere, Miiller, Entomostraca, 1785. 



Valves unequal, mostly oblong-ovate, subreniform, or quadrate ; surface variously orna- 

 mented, smooth, punctate, foveolate, strongly rugose, spinous or tuberculated, usually 

 ha\'ing a distinct polished tubercle over the anterior hinge-joint. Hinge formed on the 

 right valve by two terminal teeth, on the left by one anterior tooth, and a posterior fossa, 

 between which there is frequently a ridge which is received into a corresponding furrow 

 of the opposite valve ; the teeth are in some few cases crenulated, and on the left valve 

 are sometimes altogether absent. Antennse robust ; anterior five- or six-jointed, armed on 

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

 the fourth joint ; posterior four-jointed, the last joint short and stout; mandibular palp 

 three- or four-jointed, bearing in place of abranchial appendage a turf of two to five setse. 

 Eyes one or two. Structure of the shell usually very dense. 



The genus Cythere, as above defined, includes probably nearly as many species, recent 

 and fossil, as all the remaining genera put together, the number assigned to it in this mono- 

 graph being 8 3 out of a total of 2 2 1 . But though in its present form excessively unwieldy, 

 it seems impossible, without a more perfect knowledge than we yet possess of the varia- 

 tions of anatomical structure in the several sjDecies, either to form useful sub-genera, or to 

 separate from the main group any true generic types. I have no doubt, however, that 

 further investigation waU before long enable us to do this. Meantime it is sufficient to 

 note that the external shell characters are quite insufficient for the purj)ose, and that such 

 divisions as have already been proposed, on this basis, are at the best very vague, and can 

 only be looked upon as a mere temporary expedient for the sake of convenience. 



1. Cythere scintillulata, n. sp. (PI. XIV. fig. 3, a-d). 



Shell oblong, compressed, subreniform, rather lower in front than behind ; seen from 



