PLATE 43. 
r 
Bigs k. 260. 13. ORTHOCERAS TEXTILE. (Pag. 199.) 
| a. A fragment of the natural size. 1b. A portion of the surface enlarged, to show the strie. 
Fig. 2. 261. 14. OnrHocERAS BILINEATUM. (Pag. 199.) 
2a, b. Views of two individuals, showing the annulations and longitudinal strie. 
2. Transverse section of . 2d. Portion of the surface enlarged. 
Fig. 3. 262. 15. ORTHOCERAS BILINEATUM, var. a. (Pag. 200.) 
3 a. A fragment of this variety. 3b. Transverse section, slightly compressed, showing the siphon. 
3 e. An enlarged portion of the surface, 
3d. A fragment denuded of the shell, showing the lines of septa which do not correspond to the annulations. 
Fig. 4. 263. 16. ORrTHoCERAS CLATHRATUM. (Pag. 201.) 
4 a. The fragment, natural size. 1b. Magnified portion of the surface. 4c. Transverse section. 
Fig. 5. 264. 17. OrnrHocERAS VERTEBRALE. (Pag. 201.) 
5 a. Ventral side of the fragment. 5b. Portion of the dorsal side. 5 e. Transverse section. 
Fig. 6. 265. 18. OrrHocERAS ANELLUM. (Pag. 202.) 
6 a, A fragment of the septate portion of the shell. 6 b. Transverse section of the same. 
6 e. Enlarged portion, showing the stria, which, on a great part of the surface, are covered by a calcareous 
coating. 
6d, A smaller fragment. 6 e. Transverse section. 6 f. Portion of the surface enlarged. 
Fig. 7. 266. 19. OxntHocERAS UNDULOSTRIATUM. : (Pag. 202.) 
7 a. Ventral side of a fragment, showing the nearly transverse direction of the annulations. 
7b. Dorsal side of the same, the specimen cylindrical. 7c. Transverse section of the same. 
7d, e. Two smaller fragments of the species, compressed in different degrees. 
7f, g. Transverse sections of the two last. 7h. An enlarged portion of the surface. 
77,k. Another fragment and section, showing the position of the siphuncle. 
Fig. 8. 267. 20. Orruoceras (O. trochleare? ). (Pag. 203.) 
