EXPLANATION OF THE PLATES. 



PLATE I. 



Fig. 1. Belemnites Americanus, 



2. Transverse section of the same 



fossil, 



3. Same, subfusiform, 



3-a. Variety of the same species ? 

 Obscurely chambered, and ob- 

 tuse at the apex, 



4. Belemnites ? ambiguus, 



5. Transverse section magnified, 



6. Baculites ovatus, 



7. Transverse section of the same, 



8. Same species, 



9, 10. Anthophyllum atlanticum, 



11. Patella tentorium, 



12. Baculites asper, 



13. Transverse section, 



14. Vermetus rotula. 



PLATE II. 



Fig. 1 . Ammonites placenta, from a 

 specimen fifteen inches in 

 diameter, 



2. Septa, natural size, 



3. Ammonites Vanuxemi, 



4. Marginal view of the same, 



5. Ammonites Delawarensis, 



6. Scaphites reniformis, 



7. Ammonites telifer, 



8. Hamulus onyx. 



PLATE III. 



Fig. 1. Terebratula Harlani, 



2. Terebratula fragilis, 



3, 4. Terebratula Sayi, 



5. Ostrea falcata, 



6. Ostrea panda, 



7. Turritella encrinoides, 

 9. Ostrea plumosa, 



10. Scalaria annulata, 



11. Area rostellata, 



12. Clypeaster florealis, 



13. Turritella vertebroides, 



14. Cassidulus sequoreus, 



15. Nucleolites crucifer, 



16. Spine of Echinus, 



17. Plate of do. 



18. Young of Spatangus parastatus, 



19. Ananchytes cinctus, 



20. Ananchytes fimbriatus, 



21. Spatangus parastatus, full grown. 



PLATE IV. 



Fig. 1, 2. Gryphaea convexa, 

 3. mutabilis. 



PLATE V. 



Fig. 1. Cytherea excavata, 



2. Plagiostoma pelagicum, 



3. Tornatella bullata, 



4. Pecten anatipes, 



