PLATE LVI 



PAGE 



Figs. 1-4. RHIPIDOMELLA MUSCULOSA (Hall) 305 



1. Exterior of dorsal shell. 



2. Lateral view of the conjoined valves. 



3. Interior of dorsal valve. 



4. Interior of ventral valve. 



Oriskany formation, Ridgely member, Cumberland. (After 

 Hall.) 



Figs. 5-8. SCHIZOPHORIA MULTISTRIATA (Hall) 307 



5. 6. Dorsal and side views of shells. 



7, 8. Internal cast of ventral and dorsal valves. 

 New Scotland formation, New York. 



Figs. 9-12. SCHIZOPHORIA ORISKANIA Schuchert n. sp 307 



9, 10. Dorsal and side views. The discontinuous striae in the drawing 



are due to the pseudomorphous nature of the specimen. 

 11, 12. Internal casts of ventral and dorsal valves. 



Oriskany formation, Ridgely member, Cumberland. 



Figs. 13-17. LEPT^NA RHOMBOIDALIS (Wilckens) 308 



13, 15. Ventral and dorsal views. 

 14. Ventral valve. 



16. Interior of dorsal valve, showing some variety of character. 



17. Internal cast of ventral valve. 



New Scotland formation, New York. 



Fig. 18. LEPT.ENA RHOMPXHDAOS VAR. VEXTRICOSA (Hall) 309 



Interior view of dorsal valve. Oriskany formation, New York. 



47 



