122 A Synopsis of the Recent British Ostracpda. 



Cytheeidea, Bosquet. — Upper antennas (Fig. 8), robust, 

 five-jointed and strongly spinous, the last joint narrow and 

 elongated; lower antennas four -jointed, fiagellum long and 

 slender. Eight foot of the first and second pairs in the male 

 different from the rest, that of the first pair very strong and 

 prehensile, of the second very feeble, the apical portion rudi- 

 mentary and not clawed. Shell sub triangular, highest in 

 front, thick ; surface smooth, closely pitted, or concentrically 

 rugose. Hinge-joint formed by two crenulated elevations of 

 the right valve, which are received into corresponding depres- 

 sions of the left. Habitat, mostly marine. 



G. elongata, Brady ; papUlosa, Bosquet ; Zetlandica, 

 Brady; (?) subflavescens, Brady; jpunctillata, Brady; torosa } 

 (Jones) ; lacustris (G. 0. Sars) ; dentata, G. O. Sars. 



The genus Cyprideis, Jones, is here united with Cythe- 

 ridea. Of the species enumerated, all are marine excepting 

 0. lacustris and torosa, the former of which occurs in fresh 

 water, but seems to be excessively rare ; the latter mostly in 

 brackish, though it has in one or two instances been found in 

 fresh water. In the brackish pools of our salt marshes, and 

 amongst estuarine mud, it often occurs in prodigious numbers. 

 The powerfully chelate right foot of the first pair in the male 

 is a remarkable character of this genus, and is interesting as 

 showing a similarity of plan between this and other tribes of 

 Bntomostraca where the right and left limbs of the male 

 exhibit analogous differences of structure. Somewhat similar 

 differences occur likewise in other genera of Ostracoda, but 

 they are especially well marked in Cytheridea. It may be 

 noted that the male of C. lacustris has not yet been observed 

 either in Norway or in this country, so that its place in 

 this genus is merely provisional. Its only known British 

 habitats are the North Shaws Loch, Selkirkshire, and the 

 Glasgow and Paisley Canal, where it was found by Mr. D. 

 Robertson. 



Cytheeopsis, Gr. 0. Sars. — Antennas much as in Cythere, 

 except that the lower are much more robust. Incisive portion 

 of the first maxilla weak, internal segment rudimentary. 

 Second pair of maxillae very large and much dilated at the 

 apex, flabelliform, and beset with numerous setas. Feet alike 

 in male and female. Shell high and compressed in front, 

 depressed and tumid behind ; thin, pellucid, and marked with 

 round white papilhe. Marine. 



G. declivis (Norman), Argus, G. O. Sars. 



Ilyobates, G. 0. Sars. — Upper antennas very stout, five- 

 jointed, the first two joints much thickened. Feet very short, 

 the first two pairs three, the last four-jointed. Right foot of 

 the last pair in the male prehensile, and only three-jointed, 





