614 Contributions to Invertebrate Palaeontology. 



PLATE XL 



LiJfGULA Manni Hall. Page r)46. 



Figs. 1 and 2. Views of two dififereut individuals varying slightly in size. 

 From near Dublin, Ohio. 



LiNGULA LiGEA (?) Hall. Page 547. 

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



DisclNA MiNUTA Hall. Page 547. 



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

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



DisciNA LoDENSis Hall. Page 547. 

 Fig. 7. View of a lower valve, natural size. 



Chonetes eeversa Whitf. Page 549. 



Fig. 8. View of the specimen described showing the general form and the 



cardinal spines. 

 Fig. 9. Enlargement of the surface to show the alternating striae. 



Chonetes scitula Hall. Page 548. 



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

 shows the depth and curvature of the valves. 



Leiorhynchus limitaris Vanuxem. Page 550. 

 Fig. 11. A view of a ventral valve, natural size. c 



Gilbertsoceinus spinigerus Hall. Page 553. 

 Fig. 12. View of the anterior side of the specimen. 



Spikifera ziczac Hall. Page 554. 

 Fig. 13. View of a ventral valve, the surface exfoliated. 



Spirifera Maia Billings. Page 549. 

 Fig. 14. View of a cast of a dorsal valve. 



Pterinea .similis Whitf. Page 551. 

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



AvicuLOPECTKN ? EQUiLATERA Hall. Page 551. 

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



Pterinea flabella Conrad. Page 555. 

 Fig. 17. View of a left valve, restoi-ed on the anterior margin. 



Nyassa argcta H. and W. Page 558. 

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



