PLATE XIII 



PAGE 



Figs. 1-6. CHONETES MABYLANDICUS Prosser n. sp 157 



1. Partly exfoliated interior of dorsal valve. X 1V 2 . 21st Bridge. 



2. Interior of ventral valve. X 1%. Same locality. 



3. Exterior of dorsal valve. X 1%. Same locality. 



4. Portion of the same enlarged, showing the bifurcating striae and the 



radiating thread-like ones. X 5. 



5. Partly exfoliated interior of dorsal valve. X 2. 21st Bridge. 



6. Interior of ventral valve, showing rounded median ridge. X 1%. 



Same locality. 

 Romney formation, Hamilton member. 



Figs. 7-9. CHONETES BUGOSTJS Kindle 158 



7. Exfoliated ventral valve, showing imperfectly the subtended proc- 



esses of the mucronate spines. X 2. 



8. Type, showing a ventral valve with the peculiar spines attached 



latterly to the hinge line. X 2. 



9. Natural mold of the exterior of a ventral valve. X 2. 



Romney formation, Onondaga member, 3 miles east of Cum- 

 berland. (After Kindle.) 



FigS. 10-13. ANOPLEA NUCLEATA 159 



10, 11. Casts of two ventral valves, showing two types of medium sep- 

 tum, one terminating anteriorly in an indistinct Y-shaped proc- 

 ess. X 3. 



12. Cardinal view of natural cast of pedicle valve, showing filling of 



oblique cardinal tubes. X 5. 



13. Pedicle view. 



Romney formation, Onondaga member, Mendota, Va. ( After 

 Kindle.) 



Figs. 14-16. STROPHALOSIA TKTJNCATA (Hall) 160 



14. Exfoliated ventral valve, showing truncated umbo. X 3. Iron 



Bridge over Town Creek, northeast of Oldtown. 



15. Part of an exfoliated ventral valve. X 4. Same locality. 



16. Exfoliated dorsal valve. X 2. Evitts Creek. 



Romney formation, Hamilton member. 



Fig. 17. PRODUCTEIXA CF. SPINULICOSTA Hall 162 



Exfoliated ventral valve. X 2. Williams Road. */ mile east of Queen 

 City Hotel, Cumberland. Romney formation, Hamilton member. 



Figs. 18-20. PRODUCTELLA SPINULICOSTA Hall 162 



18. Ventral valve of a small broad form. 



19. Cardinal view of ventral valve. 



20. Small individual imbedded in the rock and showing attached 



spines. 

 Hamilton formation, New York. 



Fig. 21. PRODUCTELLA ( ?) SCHUCHERTI Prosser n. sp 163 



Imperfect ventral valve. Ernstville. 



Figs. 22-25. DALMANELLA LENTICULARIS (Vanuxem) 164 



22. Dorsal view. X 2. 



23. Interior of a dorsal valve. 



24. 25. Two fragmentary casts of ventral valves. 



Romney formation, Onondaga member, Berkeley Springs, W 

 Va. (After Kindle.) 



Figs. 26-29. RHIPIDOMELLA VANUXEMI Hall 165 



26. Ventral valve. Evitts Creek. 



27. Dorsal valve of same specimen. 



28. Interior of dorsal valve. Williams Road, */ mile east of Queen 



City Hotel, Cumberland. 



Romney formation, Hamilton member. 



29. An enlargement of the surface stria?. Hamilton formation, New 



York. 



M 



