BONES OF THE HEAD. 



Skeletox (Fig. -i). 

 Bony fishes, or Teleostet, have the elements of the skeleton well ossified. 

 They comprise all the fishes here described, except Sturg-eous and Lampreys. 

 The skull (Fig". 5) is formed upon the same g-eneral plan as the skull in any 

 other vertebrate animal, the essential difference consisting in the development 

 of the suspensory arch for the lower jaw, by the hyo-mandibular bone united 

 to the skull, and the quadrate bone which articulates with the lower jaw; 

 and these bones, with some other less important elements, support the oper- 



■ElUH WITH THE OPERCULUM KFMOYED, TO SHOW THE JiOXl 

 IE BKANCHIAL ARCHES, AND THE RRANCHI-OSTEGAL KAYS. 



or THE HEAD, 



1, Frontal ; 2, pre-frontal ; 3, post-frontal ; 4, epiotio ; 5, supra-occipital ; 6, basi-occipital ; 7, ex-occipital ; 

 9, vomer ; 10, para-sphenoid ; 11, nasal ; 12, ali- sphenoid ; 13, orLiito-spiienoid ; 15, jjetrosal ; 17, pre-maxillary; 

 18, maxillary ; 19, deutary and articular elements of mandible ; 20, hyo-maudibulur ; 21, qiiadiate ; 22, meta- 

 IJterygoid; 23, pterygoid; 24, ento-pterygoid ; 25, palatine; 26, symplectic; 27, operculum; 28, pre-oper- 

 culum ; 29, suli-operculum ; 30, inter-opercvxlnm behind the gill-rakers ; 31, stylo-hjal ; 32, epi-hval, corato- 

 hyal, and basi-hjal : 33, glosso-byal ; 34, brauchi-ostegul rays ; 35, bones of the branchial arches ; 36, uro-hyal. 



culum, which is j)eculiar to fishes. The branchial apparatus is also a dis- 

 tinctive fish character; and the hyoid, or tongue-bone, attains a remarkable 

 development in bony fishes, consisting of median pieces, from which a jointed 

 arch is given off on each side. 



There are five branchial arches (Fig. 5), but the fifth is modified, and instead 

 of supporting a gill, becomes in many genera armed with teeth, and is known 

 as the pharyngeal bone. The other branchial arches consist of three or four 

 •|)ieces. The outermost is the epi-branchial, the middle ])!ece is the cerato- 



