^ Mr. T. R. Jones on some fossil Entomostraca. 



l^yS'Vythere trigonalisj nobis. Length -j^ inch. PL III. fig. 5 a, b, c. 



Carapace-valve triangular, convex, finely punctated ; extremities 

 obliquely rounded ; the anterior much broader than the posterior 

 extremity; ventral border nearly straight ; dorsal border angular. 

 Hinge-mai^gin oblique and slightly developed. ,. gig^j^e;. §t^; 

 rower than the left. Dorsal aspect acute-ovalf -^„,[+ of-^f '^ alRfi 



A unique specimen of this interesting form occurs at Clacton, 

 and is identical with an undescribed recent species from Pegwell 

 Bay, except that the latter has teeth or blunt spines on the an- 

 terior and posterior margins, as is usual with the genus Cy there. 



A smooth form, var. lavis, which occurs plentifully at Grays, 

 differs from the Clacton specimen merely in the want of pittings. 



Cythere trigonalis approaches distantly in form some old spe- 

 cimens of Cypris tristriata, and it more nearly resembles Cythere 

 Hilseana of the cretaceous formation, but differs materially from 

 both in the structure of its hinge. .^ wort ifiw ,9m dliw ,s6i.osqe 



P.S. In a paper lately read before th^ Geofcgtcal 'Soiiet'y, Mr'. 

 " W. J. Hamilton notices the occurrence of an extensive deposit of 

 freshwater marl in the Cambridgeshire Fens, in which, in com- 

 pany with still existing land and freshwater mpllusks, the follow- 

 ing Entomostraca occur : - -iinii^^ uJ i)«£iii?>iii mii 1 fcioiijyfi ic 



Cypns minuta, Bairdr Candona lucens, Baira. 



— setigera, nobis. reptans, Baird. 



gibba, Ramdohr. i<:..j. -• ,r.,u.u... 



<) vJanfiv boiijn 

 EXPLANATION OF PLATE IIL 



]^,, J.^,,, Cypris Browniana -\- \6: a, left valve; b, right valve j c, dorsal 



. ' . profile of both valves ; d, anterior profile of both valves. ,j, 



Fiy. z.' Cypris tumida + 16 : a, left valve ; 6, dorsal profile of both valves^ 



J q i ; , c, anterior profile of both valves . 

 Fig^ du'JCypris setigera -\- 16 : a, right valve; 6, dorsal profile of both 

 5/1^1 I valves; c, anterior profile of both valves. 

 M^ j^.^^Qypris gibba + 16 : a, left valve ; b, dorsal profile of both valves; 



" c, anterior profile of both valves. , 



Tig. B. Cythere trigonalis -\- S : a, left valve; b, dorsal profile of Both 

 ' ' ' valves ; c, anterior profile of both valves. 



Fig. 6. Candona torosa -\- \6: a, left valve, young; b, left valve, adult; 

 c, right valve, adult ; d, dorsal profile of both valves, adult ; e, an- 

 terior profile of both valves, adult. 

 Fig. 7. Candona reptans + 8 : a, left valve ; b, dorsal profile of both valves ; 



>jU (Vi c, anterior profile of both valves, 

 F^r^ &i Candona lucens + 8 : a, left valve ; b, dorsal profile of both valves ; 



A- c, anterior profile of both valves. li.iqij; > 



N.B. The carapace-valves and the dorsal profiles are figured with the Wfe- 

 rior extremity upwards ; and in the anterior profiles the dorsal 

 , margins are uppermost. 



* Brit. Entom. p. 155. n. 6. tab. 18. figs. 7, 8. 



