Vol. 50.] ME. E. CHAPMAN ON THE BAEGATE BEDS OF ST7EEEY. 691 



13. Cttheeidea bipapixlata, sp. nov. (PI. XXXIII. fig. 5 a, b, c.) 



Valve subobloug ; the surface gently and almost equally convex. 

 The ventral edge is slightly steeper than the dorsal edge. The 

 anterior margin rounded, with a flattened rim, narrow, hut showing 

 a distinct fluting of the surface. The valve is decorated with some- 

 what irregular square or polygonal pittings. At the antero-dorsal 

 region are situated two round and low papillae, placed close together. 

 Length of valve J^ in. (05 mm.). 



One valve from clay of Bargate Pebble-beds, Littleton. 



14. Cytheeopteeon concenteicum (Reuss). 



Cyiherina concentrica, Reuss, ' Verstein. bohm. Kreideform.' pt. ii. 

 (1846) pp. 104 & 105, pi. xxiv. figs. 22 a-c. 



Cytheropteron concentricum, Jones & Hinde, Mon. Cret. Entom. 

 Suppl., Pal. Soc. (1890) p. 31, pi. i. figs. 5-10, pi. iv. fig. 19. 



This species has been recorded from Upper Cretaceous strata, from 

 the Neocomian of Haute Marne, and from the Upper Oolite (?) of 

 Dorset. The Bargate specimens still retain the delicate sculpturing 

 of the test-surface, and their excellent preservation leads me to 

 suppose that of these minute fossils some at least were living during 

 the deposition of these beds, and that, unlike the calcareous oolitic 

 grains found in the associated rocks, they may not have been derived 

 from older strata. 



Two valves from clay-seams of Bargate Pebble-beds, Littleton ; 

 and two from Pebble-beds of Halfpenny Lane below St. Martha's 

 Hill, Chilworth. 



15. Cytheeopteeon concenteicttm (Reuss), var. vieginea, Jones. 



Cythere punctatula (non Romer), var. virginea, Jones, Mon. Cret. 

 Entom., Pal. Soc. (1849) p. 12, pi. i. fig. 2n. 



Cytheropteron concentricum, var. virginea, Jones & Hinde, Mon. 

 Cret. Entom. Suppl., Pal. Soc. (1890) p. 32, pi. i. figs. 14-17. 



This variety is known from many Upper Cretaceous deposits 

 down to the Upper Greensand. 



One fragmentary valve from clay of Pebble-beds, Littleton. 



16. Cytheeopteeon stjbconcentbict/m (Jones). 



Cythere subconcentrica, Jones, Quart. Journ. Geol. Soc. vol. xl. 

 (1884) p. 768, pi. xxxiv. figs. 28, 29. 



This species was originally described from the Junction-bed of 

 the Oolite with the Neocomian (?) from the Richmond Well-boring. 



One valve from clay-seams of Pebble-beds, Littleton. 



17. Cytheeopteeon deupaceum (Jones). 



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

 (1884) p. 772, pi. xxxiv. fig. 30. 



This species was first described from the Great Oolite of the 

 Richmond Well-boring. 



One valve from clay-seams of Pebble-beds, Littleton. 

 Q.J.G.S. No. 200. ' 3 b 



