16 THE ENTOMOSTRACA OF 



No. 1. Cythereis interrupta, Bosquet. Tab. II, fig. 6 a — It. 



CyPKiDiNA iNTERKUPTA, Bosquet. 1847. Entom. foss. Maestricht, p. 12, n. 3, pi. ii, fig. 1. a — d. 



Var. a and /3. 

 INCH. INCH. 



Length, -jij 

 Height, Jj 

 Tliickness, -gV 



■J^ Greensand, Blackdown. Var. a. Gault, Leacoa HiU and Folkstone. 



giy Detritus, Charing. Var. p. Gault, Folkstone. 



Chalk, Woolwich. Var. y. Greensand, Farringdon. 



Chalk, Maestricht {Bosquet). Upper Oolite, Dorsetshire. 



Carapace oblong. Valves convex, slightly depressed towards the dorsal border, 

 usually pitted like the surface of a thimble ; punctation subconcentric. Anterior 

 extremity depressed, rounded, slightly bearded ; posterior narrower, subacute ; both 

 extremities having a slight marginal ridge. Superior and inferior margins nearly 

 straight ; a slight ridge sometimes present near the ventral border. Hinges very 

 slightly developed. The central and the two posterior tubercles nearly obsolete. 



Dorsal and ventral aspects somewhat oblong ; anterior extremity narrower than the 

 'posterior, strongly produced ; posterior slightly produced. Anterior aspect somewhat oval. 



This species occurs in the Charing Detritus ; it is very rare in the Chalk and the 

 Greensand. M. Bosquet describes it as occurring at Maestricht. It is found also 

 in the Upper Oolite (white limestone with flints) at Upway, Dorsetshire. 



Variety a, figs. 6<5, 6/. 

 Gault, Leacon Hill, near Charing, and Folkstone. 



In this variety the height of the valves is proportionally greater. The anterior 

 and posterior margins are bearded ; the anterior marginal ridge is strongly marked ; 

 the whole surface of the valves is bristled with fine spines ; and the punctations are 

 confined to the middle of the valves. Central tubercle is obsolete. The posterior 

 tubercles are sometimes slightly acuminate. Near the centre of the valve in this 

 and the following variety is observable (by transmitted light) a patch of 4-5 oval lucid 

 spots arranged in two little groups, 3-4 small spots in the one, and 1-2 larger spots 

 in the other group. Plentiful at Leacon Hill, near Charing, Kent. 



Variety j3, figs. 6c, %d, Qg. 

 Gault, Folkstone. 



Similar in size and shape to var. a ; the valves are setaceous ; central tubercle 

 sometimes covered with closely set, short, strong spines. Punctations more or less 

 obsolete. This variety is very plentiful in the Folkstone Gault. 



