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PAGE 



Figs. 1, 2. ORBICULOIDEA BCEDERI Schuchert n. sp 290 



1. Exterior of dorsal valve. 



2. Exterior mold of ventral valve. 



Oriskany formation, Ridgely member, Cash Valley. 



Figs. 3-5. OBBICULOIDEA AMPLA (Hall) 291 



3. Cast from a mold of the dorsal valve. 



4. Side elevation of same. 



5. Partially exfoliated ventral valve. 



Oriskany formation, New York. 



Figs. 6, 7. ORBICULOIDEA SCHUCHEBTI Swartz n. sp 292 



6. Exterior of dorsal valve. 



7. Exterior of ventral valve. 



Helderberg formation, Keyser member, Dawson, W. Va. 



Figs. 8, 9. PHOLIDOPS MULTILAMELLOSA Schuchert n. sp 293 



8. Exterior of ventral ? valve partially exfoliated, showing interior 



muscular scars. X 2. 



9. Exterior of dorsal valve. X 2. 



Oriskany formation, Shriver member, Cash Valley. 



Figs. 10-12. PHOLIDOPS OVATA Hall 294 



10. Exterior of dorsal valve. X 3. New Scotland of New York. 



11. Interior of dorsal valve. X 5. 



12. Exterior of dorsal valve. X 5. 



Helderberg formation, Keyser member, % mile southwest of 

 Rawlings. 



Fig. 13. PHOLIDOPS TUMIDA Schuchert n. sp 294 



Exterior of dorsal valve. X 3. Oriskany formation, Shriver member, 

 Winchester road. 



Figs. 14-19. LIXGULAPHOLIS TERMINALIS (Hall) 296 



14. Exterior of ventral valve. 



15. Exterior of dorsal valve. 



16. Exterior of dorsal ? valve of another specimen. X 2. 



17. Profile outline of same, showing both valves in position. 



18. Interior of ventral valve. X 2. 



19. Interior of ventral valve. X 3. 



Oriskany formation, Ridgely member, Cumberland. (Figs. 

 14, 15, 19, after Hall.) 



Figs. 20-23. ORTHOSTROPHIA STROPHOMENOIDES (Hall) 297 



20. 21. Internal casts of ventral and dorsal valves. 

 22, 23. Dorsal and cardinal views. 



New Scotland formation, New York. 



