FOSSIL CEPHALOPODS. 



321 



generally, wherever the chalk marl is worked, many 

 of these forms of Ammonitidce will be found. A good 

 many true Ammonites range to the very highest 

 part of the Norfolk Chalk, which is, perhaps, the 

 highest horizon in England such as Ammonites Rho- 

 tomagensis, etc. 



Fig. 330. Phragmoceras ventricost. 



The Belemnites belong to the Dibranchiate (or two- 

 gilled) division of Cephalopoda. The fossils known 

 by this name are the hard internal parts or " guards " 

 of an extinct family of cuttle-fishes. It will be seen, 

 in a perfect Belemnite, that the upper and thicker 



Y 



