68 D. J. seOURPIELD ON BRITISH CLADOCERA. 



Female. — Yellow or yellowish brown. Dorsal margin of 

 carapace well arched, meeting posterior at a very obtuse angle. 

 Ventral margin nearly straight, fringed with hairs, and 

 rounded behind. Shell marked with faint longitudinal ridges. 

 Simple eye about half the size of the compound, and slightly 

 nearer to it than to the tip of the rostrum. Antennae small. 

 Tail short and rounded at the end. Furnished on each side of 

 the dorsal edge with a row of minute spines in groups of three 

 or four. There is also a lateral row of teeth, but they are very 

 faint. Terminal claws with a small spine at the base. Eggs 

 usually two. Length, -^^ in. 



Found in the following localities : — Wanstead Park, Essex, 

 November, 1889, September, 1890, October, 1891 ; Cuckoo Pits, 

 Chingford, Essex, September, 1890; Victoria Park, London, 

 November, 1890 ; Eagle Pond, Snaresbrook, Essex, November, 

 1890 and 1891. 



So far, I have not seen the male. 



Chydorus ova lis, Kurz. (Plate V, Figs. 6 and 7). — The 

 genus Chydorus comprises some nine or ten recognized species, 

 of which one, G. sphericusj is extremely abundant everywhere, 

 while the remaining forms are rare and local. The former 

 consequently is well known, while the latter are very little 

 known, and probably often confounded with the common 

 species. There can be little doubt that this has often happened 

 in the case of the present species. It may be distinguished, 

 however, from C. sphericus by the absence of evident reticula- 

 tion on its more evenly ovoid shell, and by its somewhat 

 broader tail. 



Female. — Colour red. Shell oval or somewhat egg-shaped, 

 not truncate posteriorly, nor angulated ventrally. Shell 

 markings hexagonal, but so extremely ill-defined as to be 

 easily overlooked. Eye-spot nearer to the compound eye than 

 to the end of the rostrum, a little more than half the size of 

 the former. Antennules spindle-shaped, with a lateral seta 

 near the middle, and a couple of sense hairs just anterior to the 

 terminal banch. Tail rather broad, with a prominent pre-anal 

 projection. It is rounded at the extremity and armed with 

 twelve or thirteen little teeth. Terminal claws with two 

 basal teeth, the anterior of which is ver}^ minute. Eggs two. 



