EXPLANATION OF PLATE XVL 



Fig. 



40. Belemnites vulgaris. (From the Upper Lias of Whitby.) 



/. Lateral and {v) ventral aspects of an ordinary middle-aged specimen. 



/. Section across the alveolar cavity ; in this case the ventral wall is thickest. 



s". Section at the alveolar apex. 



/'. Lateral view of a young example. 



s. Longitudinal section. 



<f>. Phragmocone, in situ, of a large specimen, with short axis of guard. 



41. Lateral view of a somewhat longer individual. 



42. Belemnites rudis, n. s. (From Staithes, near Whitby.) 



/. Lateral view of an ordinary specimen ; the upper outline is supposed to be 

 the terminal edge, v and d mark the ventral and dorsal aspect at the 

 alveolar apex. 



V. Ventral aspect of the same specimen, showing the obtuse and irregular 

 groove. 



and d'. Lateral and dorsal views of a young example, more lengthened than 

 in the seniors. 

 s. Section across the alveolar chamber. 

 ft" . Section at the alveolar apex, showing great excentricity. 



Section nearer the apex of guard, showing less excentricity of axis. 



