PLATE XVI 



PAGE 



Figs. 1-3. CENTROXEIXA CF. OVATA Hall 179 



Dorsal, side and ventral view of shell. Onondaga formation, New 

 York. 



Figs. 4-6. ATRYPA RETICULARIS (Linn6) 183 



4. Partly exfoliated ventral valve (?). 



5. Dorsal valve. 



6. Ventral valve. 



Romney formation, Hamilton member, Evitts Creek. 



Figs. 7-14. TROPIDOLEPTUS CARINATUS (Conrad) 181 



7. 8. Ventral and dorsal valves of large specimen. 21st Bridge. 



9, 10. Ventral and dorsal valves of medium specimen. Same locality. 



11. Surface enlarged showing punct*. X 4. Evitts Creek. 



12. Exterior of ventral valve. 



13, 14. Interior of ventral and dorsal valves. X 2. Near Tonoloway 

 Ridge, Washington County. 



Romney formation, Hamilton member. 



