PLATE XXXI 



PAGE 



Figs. 1-5. MODIELLA PYGM.EA (Conrad) 261 



1. Right valve upon which the fine radiating striae are faintly shown. 



X 2. Evitts Creek. 



2. External impression of right valve. X 2. Evitts Creek. 



3. Internal impression of left valve, showing anterior muscular scar 



and oblique sinus. X 1%. Hill 3 miles south of Cumberland in 

 West Virginia. 



4. Cardinal view of same specimen. X I 1 /!- 



Romney formation, Hamilton member. 



5. Left valve showing fine radiating stria?. X 2. Hamilton formation, 



New York. 



Fig. 6. NYASSA ABGUTA Hall (?) 262 



Internal impression of a broken left valve, showing impressions of 

 posterior lateral teeth. Romney formation, Hamilton member, 

 McCoys Ferry. 



Figs. 7-9. NYASSA ARGUTA Hall 262 



7, 8. Right and left valves. 



9. A squeeze showing the appearance of the interior of the right valve. 



Hamilton formation, New York. 



Figs. 10, 11. AVICULOPECTEN PRINCEPS (Conrad) 263 



10. A specimen preserving both valves. 



11. A large left valve, much extended posteriorly. 



Hamilton formation, New York. 



Fig. 12. AVICULOPECTEN sp 266 



An incomplete right valve. Romney formation, Hamilton member, 

 near Hancock. 



