264 



34. CYTHERIDEA OBOVATA, Sp. .11, 



PI. ii., figs. G a, b, c. 



Smooth and very convex ; obovate, the anterior being broader 

 than the posterior ; nearly symmetrical, but the dorsal margin is 

 more rounded than the ventral. Edge view, long oval ; end 

 view, ovate. A slight notch (not shown in the figure) marks the 

 junction of the anterior and the ventral margins. The hinge- 

 ment in the specimen from which our figures are taken is 

 beautifully perfect, and consists of two crenulated ridges, running 

 side by side and gradually dying away in the middle third of the 

 hinge-line. This is precisely the same feature as seen in Cytheridea 

 pinguis, Jones, Monogr. Tert. Entom., Pal. Soc, 1856, p. 43, 

 pi. ii., figs. 4 e, 4/. 



Two or three examples ; Yellow Fullers-earth Clay, Midford. 



The side view of this form seems to have a close resemblance 

 to that of Terquem's jBaw-tiia affinis (op. cit. p. 8, pi. i., fig. 1); 

 but there is no real affinity between the two. 



35. CYTHERIDEA SPINIGYRATA, sp. U. 



PI. ii., figs. 7 a, b, c. 



Near Cythere drupacea, Jones (Quart. Journ. Geol. Soc, vol. xl., 

 1884, p. 772, pi. xxxiv., fig. 30), but the posterior end is much 

 broader, and the ornament is more distinctly gyrate, with prickles 

 instead of pits. It is also denticulate on the front margin. 



Swollen in posterior ventral region. Hinge-line distinct, and 

 longer than in C. drupacea. Hingement, that of pi. i., fig. 2. 

 Edge-view, long-ovate ; end view, ovate. 



One specimen only; Blue Fullers-earth Clay, Midford. 



36. CYTHERIDEA SPINIFASTIGIATA, Sp. 11. 



PI. ii., figs. 8 a, b, c. 

 This belongs to the same group as the last. It is much swollen 

 in the ventral region^ the swelling hiding the incurved margin. 



