PLATE VII. 



PAGE. 



Figs 1-2. Lingula Manni Hall • 441 



1 and 2. Views of two different individuals varying slightly in size. From near Dub- 

 lin, Ohio. 



Figs. 3-4. Lingula LIGEA (?) Hali 441 



3 and 4. View of a specimen natural size and enlarged. 



Figs. 5-6. Discina minuta Hall 442 



5. View of a lower valve enlarged to three diameters. 



6. View of an upper valve enlarged to the same extent. 



Fig. 7. Discina Lodensis Hall 442 



7. View of a lower valve, natural size. 



Figs. 8-9. Chonetes reversa Whitf 443 



8. View of the specimen described showing the general form and the cardinal spines. 



9. En argement of the surface to show the alteraating striae. 



Fig. 10. Chonetes SCituea Hall 443 



10. View of a specimen referred to this species, the diagram at the side shows the 

 depth and curvature of the valves. 



Fig. 11. Leiorhynchus limitaris Vanuxem 444 



11 A view of a ventral valve, natural size. 



Fig. 12. GlLBERTSOCRINUS SPINIGERUS Hall 444 



12. View of the anterior side of the specimen. 



Fig. 13. Spirifera ziczac Hall 448 



\-i. View of a ventral valve, the surface exfoliated. 



Fig. 14. Spirifera Maia Billings 447 



14. View of a cast of a dorsal valve. 



Fig. 15. Pterinea similis Whitf. 445 



15. View of a left valve showing form and surface markings 



Fig. 16. AVICULOPECTEN ? EOUIEATERA Hall 445 



16. View of an impression of a left valve enlarged. 



Fig. 17. Pterinea flabella Hall 449 



17. View of a left valve restored on the anterior margin. 



Fig. 18. Nyassa arguta H. and W 451 



18. View of a right valve showing the general form. 



Fig. 19. Grammysia bisuixaTa Conrad 451 



19. A right valve, natural size. 



Fig. 20. ACTINODESMA SUBRECTA Whitf. 450 



20. Impression in the stone of a left valve. 



