10 SIRENOID AND CROSSOPTERYGIAN GANOIDS. 



[Vomer.] 



[Pre-maxilla.] 



[Maxilla.] 



V. Ossifications of 1st Post-oral arch (Mandibular). 



Metapterygoid. 



Quadrate (Malleus of Mammalia). 



[Squamosal = pre-opercular -j- supratemporal.] 



Articular. 



[Dentary.] 



[Splenial.] 



[Angular.] 



[Coronoid.] 



[Surangular.] 



[V a. Membrane-bones of Opercular Eold. 



Pre-opercular (not differentiated in Ganoids, except Amid). 

 Inter-opercular. 



Opercular (c. Hyo-mandibular). 

 Sub-opercular.] 

 * # * The pre-opercular and inter-opercular are related to the mandibular pier, the 

 opercular and sub -opercular to the hyo-mandibular. 



VI. Ossifications of 2nd Post-oral arch (hyoid). 

 * Anterior Division. 



Hyo-mandibular (Incus of Mammalia and Columella of Amphibia. The 



Columella of Sauropsida = Incus -f- Stapes) (c. Opercular). 

 Symplectic (c. Quadrate). 

 ** Posterior Division. 

 Stylo-hyal. 

 Epi-hyal. 

 Cerato-hyal. 

 Hypo-hyal. 

 Genio- or Basi-hyal. 



[Branchiostegal Rays. Represented by cartilaginous rays in the Sharks 

 and Skates.] 



VII. Ossifications of 3rd Post-oral arch (branchial). 

 Pharyngo-branchial. 

 Epi-branchial. 



