18 PLATE IX. [Assembly 



Fossils of the Lower Helderberg group.=^ 



A. From the Waterlime series ( p. 68). 



1. Spirifer plicatus. 



2. avicula rtjgosa. 



3. Tentaculites ornatus. 



4. LiTTORINA ANTIQUA. 



5. Atrtpa sulcata. 



6. Cytherina alta. 



B. From the Pentamerus limestone ( p. 58). 



7. Pentamerus galeatus. 



8. Same, front view. 



9. euomphalus profundus. 



10. Atrypa lacunosa, 



11. Lepocrinites gebhardi. 



C. From the Catskill shaly limestone ( p. 58). 



12. Atrypa singularis, side and rear views. 



13. Eatonia medialis. 



14. Spirifer macropleura. 



15. Meristella l^vis, front and side views. 



16. Strophomena punctulipera. 



17. Strophomena radiata. 



This group is made up of the three limestones above specified. 



