PHYLUM MOLLUSCA 



259 



■ Si ph uncle 



1 __ - ' ^ Jepta 



Fig. 147. — Sectional view of internal structure of Nautilus. 



Cyrtoceracone 



Orthoceracone 



Qyroceracom 



Goniatlte 



Ceratite 



Ammonite 



Fig. 148. — Evolution of the cephalopods. 



