PLATE XXIII 



PAGE 



Figs. 1, 2. GRAMMYSIA CIRCULAKIS Hall 220 



Right and left valves partly exfoliated, showing muscular scars and 

 pallial line. Hamilton formation, New York. 



Fig. 3. GRAMMYSIA CIRCULARIS (?) Hall 220 



Left valve. Romney formation, Hamilton member, 21st Bridge. 



Fig. 4. BUCHIOLA HALLI Clarke 225 



Left valve showing the conspicuous concentric ridges on the plications. 

 X 2. Romney formation, Hamilton member, Evitts Creek. 



Fig. 5. PANENKA CF. DICHOTOMA Hall 224 



View of a fragmentary right valve. Romney formation, Onondaga 

 member, Oldtown. 



Figs. 6-10. NUCULA CORBULIFORMIS Hall 226 



6. Right valve. X 1%. Right bank of Potomac River, about 3 miles 



below Cumberland. 



7. Left valve of same. 



8. Right valve. X 1%. Same locality. 



9. Cardinal view of internal impression showing hinge crenulations. 



X l 1 /^. Same locality. 



10. Right valve showing varices of growth and concentric striae. Evitts 

 Creek. 



Romney formation, Hamilton member. 



Fig. 11. PANENKA CF. MULTIRADIATA Hall 225 



View of a large right valve showing strong radii. Hamilton formation, 

 New York. 



106 



