DESCRIPTION OF THE PLATES. 
Fig. 8. The magnified spines of the preceding shell. 
9. T. aliformis. 
10. T. rudis. 
11. T. rugosa. 
12. A calcedonic cast of a shell of the genus Trigonia. 
13. T. sinuata. 
14. The inner surface of the flat valve of Harpax. 
convex valve. 
Ifi. A magnified view of the hinge teeth of the flat valve. 
I - convex valve. 
18. A magnified view of the outside of the flat valve. 
PLATE XIII. 
Fig. 1. A fossil shell of the genus Cueullaa. 
2. Crassatella tumida. 
3. A calcedonic shell, resembling Cardium ceolicum. 
4. A rostrated shell, perhaps of the genus Tellina. 
5. Cyclus deperdita, with crenulated teeth. 
6. A donax-formed fossil shell from Gloucestershire. 
7. Another fossil shell, supposed to be of this genus. 
8. Another fossil shell, apparently of this genus. 
9. The inside of Trigonellites lata. 
10. The inside of Trigonellites lamellosa. 
11. The outside of Trigonellites lamellosa. 
12. The outside of Trigonellites lata. 
13. Erycina la-vis, on the inside. 
. on the outside. 
15. Outside of Venericardia senilis from Essex. 
16. An uncommonly marked fossil bivalve from Bedfordshire. 
17. Inside of Venericardia senilis. 
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