PLATE IV. [Assembly 



Fossils of the Hudson-river group. 



1. LiNGULA QUADRATA. 



2. Strophomena ALTERNATA. 



3. MODIOLOPSIS ANODONTOIDES. 



4. NUCITLA. 



5. Ntjcfla poststriata. 



6. avicula insueta. 



7. Ambonychia radiata. 



8. Same, profile view. 



9. Cast of tlie same. 



10. MODIOLOPSIS MODIOLARIS. 



11. Same. 



12. Trinucleus concentrious, perfect specimen. 



13. Taiarthrus beckii ( p. 49). 



