EXPLANATION OF THE PLATES. 
5. Pecten perplanus, 
6. Plagiostoma gregale, 
7. Pecten venustus, 
8. Rostellaria arenarum, 
9. Nummulites Mantelli, 
10. Anomia argentaria, 
8. Terebratula Harlani, var. dis- 
coidal, 
9. Same, var. rectilateral, 
10. Pholas cithara, 
11, Clavagella armata. 

11. Anomia tellinoides. PLATE X. 
Fig. 1. Ostrea torosa, 
PLATE VI. 2. Plicatula urticosa, 
Fig. 1 represents the inside of the lower 3. Pecten calvatus, 
valve, and the back of the A, membranosus, 
upper one, of Exogyra cos- 5. Balanus peregrinus, 
tata, 
2. Back of lower valve, 
3. Hinge of upper valve, 
4, Hinge of lower valve. 
PLATE VII. 
Fig. 1. Scaphites hippocrepis, vel Cu- 
vierl, 
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. Gryphea vomer, (young shell,) 
5. Gryphea vomer, (adult.) 
6. Ostrea falcata, var. nasuta, 
7. Same species, var. mesenterica, 
6. Spatangus ungula, 
7. Echinus infulatus, 
8. Scutella Lyelli, 
9. Clypeaster 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 Sphyrena, 
2, 3, 4. Teeth of sharks. 
PLATE XIII. 
Fig. 1. Baculites carinatus, 

