PLATE XVII 



PAGE 



Figs. 1-9. CYRTINA HAMILTOXEXSIS Hall 185 



1. Interior of ventral valve distorted by crushing. McCoys Ferry. 



2. Cardinal area of same, showing delthyrium. 



3. Interior of dorsal valve. McCoys Ferry. 



4. Dorsal valve. McCoys Ferry. X 1%. 



5. Enlarged part of shell showing its structure. X 4. National Road 



northeast of Cumberland. 



6. Cardinal area of ventral valve. X 2. Near Hancock. 



7. 8. Internal casts of ventral valve. Near Hancock. 



Romney formation, Hamilton member. 



9. Dorsal valve and cardinal area of ventral valve, showing the 



elongate foramen on the deltidial plate. Hamilton formation, 

 New York. 



Figs. 10-18. SPIRIFEB MUCRONATUS (Conrad) 187 



10. Ventral valve. Evitts Creek. 



11. Dorsal valve of same. 



12. Interior of ventral valve. Iron Bridge over Town Creek, northeast 



of Oldtown. 



13. Interior of dorsal valve. Same locality. 



14. Interior of partly exfoliated dorsal valve. McCoys Ferry. 

 15-17. Exteriors of ventral valves. Near Hancock. 



18. Interior of ventral valve. Near Hancock. 



Romney formation, Hamilton member. 



