EXPLANATION OF THE PLATES. 



5. Pecten perplanus, 



6. Plagiostoma gregale, 



7. Pecten venustus, 



8. Rostellaria arenarum, 



9. Nummulites Mantelli, 



10. Anomia argentaria, 



11. Anomia tellinoides. 



PLATE VI. 



Fig. 1 represents the inside of the lower 

 valve, and the back of the 

 upper one, of Exogyra cos- 

 tata, 



2. Back of lower valve, 



3. Hinge of upper valve, 



4. Hinge of lower valve. 



PLATE VII. 



Fig. 1. Scaphites hippocrepis, vel Cu- 

 vieri, 

 2, 3. Crepidula costata, from the 

 Upper Marine formation of 

 St. Mary's, Maryland. 



PLATE VIII. 



Fig. 1. Venilia Conradi, showing the 

 hinge in each valve, 



2. Lateral view, 



3. Pholadomya occidentalis, 



4. Nautilus Dekayi. 



PLATE IX. 



Fig. 1. Baculites compressus, 



2. Teredo tibialis, 



3. Cardita decisa, 



4. Gryphaca vomer, (young shell,) 



5. Grypheca vomer, (adult.) 



6. Ostrea falcata, var. nasuta, 



7. Same species, var. mcscntcricu, 



8. Terebratula Harlani, var. dis- 



coidal, 



9. Same, var. rectilateral, 



10. Pholas cithara, 



11. Clavagella armata. 



PLATE X. 



Fig. 1. Ostrea torosa, 



2. Plicatula urticosa, 



3. Pecten calvatus, 



4. membranosus, 



5. Balanus peregrinus, 



6. Spatangus ungula, 



7. Echinus infulatus, 



8. Scutella Lyelli, 



9. Clype aster geometricus, 



10. Cidaretes diatretum, 



11. Terebratula lacryma, 



12. Clypeaster florealis, 



13. Conus gyratus. 



PLATE XI. 



Fig. 1, 2, 3, 4, 5, 6 and 11, shark's teeth, 



7. Tooth, uncertain, 



8. Fragments of two teeth attach- 



ed to a fragment of bone 

 without alveoli, 



9. Mosasaurus tooth, 



10. Two teeth and portion of the 

 jaw of Geosaurus, 



12. Tooth of a crocodile, striated, 



13. Tooth of a crocodile, smooth. 



PLATE XII. 



Fig. 1. Tooth of a Sphyrcena, 

 2, 3, 4. Teeth of sharks. 



PLATE XIII. 



Fig. 1. Baculites car hiatus, 



