PLATE XVIII 



PAGE 



Figs. 1-6. SPIRIFER GRANULOSUS (Conrad) 190 



1. Ventral valve. 21st Bridge. 



2. Interior of ventral valve. Flintstone Creek in Gilpin. 



3. Interior of dorsal valve of same specimen. 



4. Enlarged portion of surface from sinus of ventral valve, showing 



the small granules. X 2. Evitts Creek. 



5. Same more highly magnified. X 8. 



Romney formation, Hamilton member. 



6. An enlargement of the surface, showing its papillose character. 



Hamilton formation, New York. 



Figs. 7-9. SPIRIFER AUDACULUS (Conrad) 192 



7. Ventral valve, partly exfoliated. Evitts Creek. 



8. Interior of ventral valve. Warrior Mountain, east of Rush. 



9. Interior of dorsal valve and cardinal area of ventral valve. West- 



ern Maryland. 



Romney formation, Hamilton member. 



Fig. 10. SPIRIFER ACUMINATUS (Conrad) 193 



Interior of broken dorsal valve. McCoys Ferry. Romney formation, 

 Hamilton member. 



101 



