PLATE LV 



PAGE 



Figs. 1-5. TROPIDOLEPTUS CARINATUS (Conrad) 585 



1. Ventral valve. Williams Road, 3% miles east of Cumberland, 1466. 



2. Cast of interior of ventral valve. Sideling Hill Creek, 2% miles 



above mouth, 1700. 



3. Dorsal valve. Two miles north of mouth of Town Creek, 1949. 



4. Interior of dorsal valve. Same locality as preceding specimen. 



5. Enlargement of hinge of fig. 4. X 4. 



Jennings formation, Parkhead member. 



Figs. 6-11. ATRYPA RETICULARIS (Linne") 586 



6. Ventral valve showing alation about margin unusually well. Jen- 



nings formation, Woodmont member, Ithaca fauna, National 

 Road, east of Hancock, 690. 



7. Enlargement of hinge of cast of interior of ventral valve. X 2. 



Same specimen as fig. 6. 



8. Enlargement of hinge of cast of interior of dorsal valve. X 3. 2y 2 



miles northeast of Pratt. 



9. Cardinal region of the dorsal valve enlarged, showing the crenulate 



dental sockets. Polish Mountain. 



10. Ventral valve retaining parts of concentric lamellae. Near Deer 



Park. 



11. Ventral valve. Oakland. 



Jennings formation, Chemung member. 



Figs. 12, 13. ATRYPA SPINOSA Hall 587 



12. Ventral valve. 



13. Cast of interior of dorsal valve. 



Jennings formation, Chemung member, Ellerslie, Penna,, 1524. 



Figs. 14-19. ATRYPA HYSTRIX Hall 589 



14. A young ventral valve. National Road, 5 miles west of Frostburg. 



15. Cast of interior of ventral valve with very coarse plications. % 



mile southwest of Gortner. 



16. Ventral valve. Trout Creek, Oakland. 



17. Dorsal valve. Near Oakland. 



18. Enlargement of surface showing the lamellae enfolding into spines. 



X 2. 



19. Ventral valve. Trout Creek, Oakland. 



Jennings formation, Chemung member. 



138 



