478 



TELEOSTEI 



[CH. 





downwards and is united to its fellow in the mid-ventral line by 

 a median piece or copula. 



The upper segment is ossified by the hyomandibular bone 

 above, which articulates with the pterotic, and the sy m p lee tic below, 

 which is firmly joined to the quadrate. The lower segment begins 

 with a small cylindrical inter hyal bone to which succeeds an 

 epiceratohyal, then the main part of the arch is ossified by a great 

 curved ceratohyal which slants forward and downward. Beneath 

 this is the small hypo hyal which is joined to its fellow by the 



FIG. 235. Mandibular and hyoid arches of a Cod, Gadus morrhuax^. 



1. Palatine. 2. Entopterygoid. 3. Pterygoid. 4. Quadrate. 



5. Symplectic. 6. Metapterygoid. 7. Hyomandibular. 8. Angular. 



9. Articular. 10. Dentary. 11. Interhyal. 12. Epihyal. 



13. Ceratohyal. 14. Hypohyal. 15. GlossohyaL 16. Branchiostegal 

 rays. 



median glossohyal which forms the copula or connecting piece 

 between the two sides of the arch. The succeeding visceral arches 

 are called branchial because they bear the gills. These arches 

 are segmented in the same way as the hyoid. Each begins above 

 with a bone termed the pharyngobranchial which frequently 

 indeed typically bears teeth, and which extends horizontally inwards 

 towards the mid-dorsal line in the dorsal wall of the pharynx. The 

 pharyngobranchials collectively are sometimes termed the superior 

 pharyngeal bones. The pharyngobranchial is succeeded by a 



