EXPLANATION OF PLATE IL 



Fig. 



4. Belemnites excavatus. 



V. Ventral aspect. (Prof. Phillips's specimen.) 



/. Lateral aspect ; d and v mark the dorsal and ventral portions. The apex of 



the alveolar cavity is between those letters. (Prof. Phillips's specimen.) 

 s. Longitudinal section, showing the very thin sheath and very deep and 



ample alveolar cavity. (Dr. Buckland's specimen.) 

 s' . Transverse section across the alveolar cavity and guard. (Prof. Phillips's 



specimen.) 

 s" Transverse section of the same specimen near the apex. 



5. Belemnites calcar. 



/', /". Lateral views of the specimen belonging to the Geological Survey (No. 612). 

 d. Dorsal view of the same. 



s. Transverse section of the same. ' 



s. A rather oblique section across the alveolar cavity, in consequence of which 



the sheath appears thicker towards the apex than it would appear on a 



truly axial section. (Oxford Museum.) 

 /"' Lateral view of a specimen supposed to be of this species. Geological 



Survey Collection (No. 613). 



6. Belemnites dens. 



/. General figure, seen laterally. The specimen is compressed, as may be seen 

 by the transverse sectional outline, s'. 

 The striae are seeil magnified at o-' and a" . 



