PLATE IX 



PAGE 



Figs. 1-7. CRANIELLA HAMILTOXM: Hall 131 



1. Internal impression of dorsal valve. X 1%. 



2. Upper or dorsal valve from which the shell is gone near the margin. 



X 2. 



3. Enlargement of part of preceding showing the finely punctate shell 



structure. X 6. 

 Romney formation, Hamilton member, Evitts Creek. 



4. Interior of a lower valve attached to a Streptelasma. 



5. Three individuals of different sizes, attached to the surface of 



Tropidoleptus carinatus. 



6. Dorsal valve. 



7. Internal impression of dorsal valve. X 2. 



Hamilton formation, New York. 



Fig. 8. PHOLIDOPS HAMILTONI.E Hall 132 



Interior of valve. X 8. Romney formation, Onondaga member, Wil- 

 liams Road, 3% miles southeast of Cumberland. 



Figs. 9, 10. PHOLIDOPS CF. AREOLATA (Hall) 133 



9. Cast of the ventral valve. 



10. Internal cast of the ventral valve. The slender impressed median 

 line of the figure has about twice the proper length. It is con- 

 spicuous only near the apex of the crescent-shaped depression. 

 X5. 



Romney formation, Onondaga member, Bells Valley, Virginia. 

 (After Kindle.) 



Figs. 11-17. STROPHEODONTA (LEPTOSTROPHIA) PERPLAXA (Conrad) 134 



11. Partly exfoliated interior of dorsal valve. Iron Bridge over Town 



Creek, northeast of Oldtown. 



12. Apparently exfoliated interior of dorsal valve, same locality. 



13. Internal impression of small ventral valve. X 1%. Williams Road, 



% mile east of Queen City Hotel, Cumberland. 



14. Further enlargement of preceding specimen, showing crenulated 



hinge-line. X 3. 



15. Internal impression showing median ridge. Iron Bridge over Town 



Creek, northeast of Oldtown. 



16. Internal impression of ventral valve showing muscular impres- 



sions. McCoys Ferry. 

 Romney formation, Hamilton member. 



17. An enlargement of the striae. Hamilton formation, New York. 



