12 PLATE VI. [Assembly 



Fossils of the Clinton group. 



1. Orthis circulus, side and end views. 



2. Atrypa congesta, side and front views. 

 8. A. NAVIFORMIS, do. do. 



4. A. PLICATULA. 



6. Joint of crinoidal stem, natural size and magnified. 



7. Pentamerus oblongus, young shell ( p. 63). 



8. Same, old shell. 



9. Same, profile view. 



10. Same, internal cast* of lower valve. 



11. Same, do. do. of upper valve. 



The dark cavities in the last two figures show where the peculiar 

 internal plates of the shell were placed. 



12. Strophomena rugosa. 



13. Fucoides biloba. 



* For explanation of a '^ cast", see p. 27. 



