THE TERTIARY FORMATION. 13 



In this species the dorsal edge is more angular, owing to the greater definition of 

 the hinge-line, than in Cypris aurantia, Jurine, sp., to which C. setigera is nearly allied 

 in general form. 1 



Its ventral margin, also, is somewhat more inturned. The very spinous surface, so 

 well preserved even in the fossil state, is markedly characteristic, in comparison with 

 the partial distribution of setse in C. aurantia. Its lucid spots are altogether differently 

 arranged from those in the last-mentioned species, in which there are eight, forming a 

 set of four, irregular, parallel, oblique lines (System a). And lastly the valves are 

 smaller and somewhat less gibbose than those of C. aurantia. 



No. 2. Cypris Browntana, Jones. Plate I, fig. 1 a — 1 d. 



Cynus Browniana, Jones. Annals and Mag. Nat. Hist., 2d ser., vi, p. 25, t. 3, fig. 1. 



INCH. 



Length, -g\ Pleistocene : Clacton, Essex. 



Carapace short and broad, somewhat square : valves convex, depressed anteriorly, 

 smooth, with a few scattered pedicles of setse ; edges of the valves rather thickened ; 

 inner marginal plate well developed : hinge-line occupying the central third of the 

 dorsal border : left valve sub-quadrangular, obliquely rounded anteriorly, semicircular 

 behind ; ventral border and central third of dorsal border almost straight : right valve 

 smaller than the left, sub-reniform. Lucid spots six, placed according to System b. 



Dorsal aspect elongate and obtuse ovate; anterior, broad ovate. 



Plentiful in the fresh-water deposit at Clacton, in Essex. 



For these and other specimens of Entomostraca from Clacton I have to thank 

 John Brown, Esq., F.G.S., of Stanway, near Colchester, who has assiduously worked 

 out the fossil fauna of the Clacton, Copford, and other Pleistocene and Post-tertiary 

 deposits, and after whom the species under notice has been named . 



Var. tumida, Jones. Plate I, fig. 2 a, 2 h. 



Cypris tumida, Jones. Annals and Mag. Nat. Hist., 2d ser., vi, p. 26, t. 3, fig. 2. 



INCH. 



Length, -^ Pleistocene : Grays, Essex. 



1 Cypris pubescens, Koch, 'Deutsch. Crust.,' 1837, Heft xi, t. 6 ; C. ovato-conchacea, De Geer, sp., 

 'Hist. Insect.,' vii, t. 29. figs. 5 — 7; C. conchacea, Jurine, sp., 'Hist. Monocl.,' t. 17, fig. 7; and C. 

 conchacea, Koch, ' Deutsch. Crust.,' 1838, Heft xxi, t. 12 — 14, also more or less resemble the species under 

 notice. 



