PLATE IV. 



Fig. 

 1. Cythereis Ceratoptera, p. 39. 

 Left valve, outside 



X 25 Crag. 



2, 3. Bairdia subdeltoidea, p. 52. 



2 a. Left valve, outside . . . x 12 



2 b. Portion of surface, showing the lucid spots and fine papillae x 75 



3. Right valve, inside (small individual) . . . x 



Cras 



12 1 



4. Cytherideis Jiavida, p. 50. 



a. Right valve, outside (narrow var.) 



b. Perfect, dorsal aspect 



c. Perfect, end view 



5. Cytherideis Ren, p. 51. 



a. Left valve, outside 



b. Left valve, dorsal view 



6. Cytheridea Sorbyana, p. 44. 



a. Right valve, outside 



b. Right valve, ventral view 



c. Right valve, anterior view 



d. Left valve, hinge-line 



e. Part of surface, showing reticulations and perforations 



7. Cythere concinna, p. 29. 



a. Right valve, outside 



b. Right valve, ventral view 



c. Right valve, anterior view 



d. Right valve, hinge-line 



e. Left valve, hinge-line 

 /. Part of surface, showing pittings and perforations 



x 25 





. x 25 

 x 25 \ 



Crag. 





x 25 1 

 x 25 J 



Crag. 



x 25 , 





x 25 





. x 25 



Bridlington 



. x 55 





. x 150 





. x 25 





. x 25 





. x 25 

 x 25 



) Bridlington. 



. x 25 





. x 150 





8, 9, 11. Candona Forbesii, p. 18. 



8. Right valve, outside (somewhat distorted) 



9. Left valve, outside 

 11a. Right valve, outside 



18 6. Right valve, ventral view 



I) 



x 12 

 x 12 K 

 x 12 



x 12 



Hordwell. 



10. Cytherideis unisulcata, p. 48. 

 Cast of right valve 



x 16 Cliff End. 



12. Candona Richardsoni, p. 18. 



a. Left valve, outside 



b. Left valve, ventral view 



L Woolwich, 

 x 25 J 



