EXPLANATION OF PLATE XXX. 



Fig. 



74. Belemnites sulcatus. Specimens of full size from the Oxford Clay of St. 



Neot's ; presented by Mr. J. F. Walker, of Sidney Sussex College, Cambridge ; 

 /, lateral view, showing a very slight flattening ; v, ventral aspect, showing the 

 groove widening and growing shallow over the alveolar region, partially inter- 

 rupted toward the apex, with striation parallel to the groove ; s, cross section 

 of guard, slightly depressed. 



75. Specimens from Weymouth, v, ventral surface, showing the groove growing 



wider and shallower both toward the apex and over the alveolus ; d', dorsal 

 aspect ; s, cross section of guard nearly round Fig. 75, lateral view of 

 another specimen, showing a slight flattening ; v", ventral aspect, the groove 

 widening over the alveolar and apicial regions, with striae of decomposition 

 parallel to the groove ; s", alveolar cross section ; s", cross section of guard. 



