PLATE 83. 
Fig. 1. 236. 13. Murchisonia gracilis. (Pag- 303.) 
1 a. A specimen (a cast) from the calcareous sandstone. 1 b. A similar cast from the soft shales at Loraine. 
1 c. A fragment of slate, with several small specimens. 
Fig. 2. 363. 14. Murchisonia uniangulata, var. abbreviata. {Pag. 304.) 
2 a , b< Two specimens which preserve a part of the shell. 
2 c. A portion of the surface of the last volution magnified, showing the double spiral band. 
2 d. A specimen with the volutions more acutely angulated, but apparently identical. 
Fig. 3. 225. 13. Pleurotomaria subconica. (Pag. 304.) 
3 a. A specimen preserving .the vertical striae. 3 b. A portion of the same enlarged. 
3 c, d. Imperfect casts, from the shales of the Hudson-river group. 
3 e. A more perfect cast of the same species, from Wisconsin. 
Fig. 4. 364. 17. Pleurotomaria [?] bilix. {Pag. 305.) 
4 a. A small specimen of this species, showing the back of the spire, and the expansion of the last volution 
towards the aperture. 
4 b. A portion of the surface enlarged, showing the alternating larger and smaller carinae, whieh are crossed 
by the oblique fine striae. 
4 c. A larger specimen : a view from the outside obliquely into the aperture. 
4 d. Another specimen, showing the form of the aperture, which is entire on the outer margin. 
4 e. The base, viewed in the direction of the spire. 
Fig. 5. 365. 18. Pleurotomaria (Species undetermbved). (Pag. 305.) 
5 a, b. Views of the apex and base of two small casts. 
Fig. 6. 366. 2. Metoptoma? rugosa. (Pag. 306.) 
6 a. Upper surface of the shell. 6 b. Lateral view. 6 c. Enlarged portion of the surface. 
Fig. 7. 239. 2. Carinaropsis patelliformis. (Pag- 306.) 
7 a. A large individual of this species. 
7 b. Profile of the same. The elevation of the shell is less than usual, from compression. 
Fig. 8. 367. 3. Carinaropsis orbiculatus. (Pag. 306.) 
8 a. View of a specimen, looking upon the apex. S b . Lateral view of specimen partially distorted. 
§ c. A portion of the surface enlarged. 
Fig. 9. 240. 1. Bellerophon bilobatus. (Pag. 307.) 
9 a. A large imperfect specimen. 
9 b, c. Lateral and profile view of a smaller specimen, showing the volutions compressed. 
Fig. 10. 368. 4. Bellerophon cancellatus. (Pag- 307.) 
10 a. Lateral view of an entire individual. 
10 b. A portion of the surface enlarged, showing the cancellated striae. 
10 c. A fragment of a shell, apparently of the same species. 
