DESCRIPTION OF THE PLATES. 
Fig. 8. 
9. 
10 . 
11 . 
12 . 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20 . 
21 . 
22 . 
23. 
24. 
25. 
26. 
27. 
28. 
29. 
30. 
31. 
32. 
Spirolinci depressa. 
Spirolina cylindracea. 
A supposed variety of the preceding fossil. 
Miliolites ringens. 
| The upper and under surfaces of Miliolites saxorum. 
^ Different views of M. cor anguinum. 
^ Different views of M. trigonule. 
M. opposita. 
Renulinites opercularia. 
The bellied semilunar worm-shell of Mr. Walker, introduced for the sake of comparison 
with the preceding. 
Gyrogonites. 
A detached carinated rib of Gyrogonites. 
A minute nautilite, resembling N. crispus, Linn, from the Appenines. 
Another minute nautilite from the same place. 
A minute fossil shell, N. Beccarii, from the Appenines, resembling the minute recent 
shells which have been supposed to be recent ammonia?. 
A reversed shell of the same species. 
An arcite, of an uncommon form, from Germany. 
A fossil shell, with a pellucid border, from the Appenines. 
A microscopic pinnite, approaching to Pinna saccata. 
A mytulite, the surface resembling a leaf. 
PLATE XII. 
Fig. !• The structure of the hinge of the right valve of Trigonia. 
2. That of the hinge of the left valve. 
3. Trigonia clavellata. 
4. T. costata. 
5. T. eccentrica. 
6. T. dadalcea. 
7. T. spinosa. 
