BONES OP THE HEAD. <) 



SKELETON (Fig. 4). 



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

 They comprise all the fishes here described, except Sturgeons and Lampreys. 

 The skull (Fig. 5) is formed upon the same general 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 bon/e 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- 



11. 



Fig. O. SKULL OF VERCH WITH THE OPEHCULtM REMOVED, TO SHOW THE HONES OF THE HEAD, 



THE BRANCHIAL ARCHES, AND THE BRANCHI-OSTEGAL RAYS. 



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

 9. vonier ; 10, para-sphenoid ; 11, nasal ; 12, ali-sphenoid ; 13, orbito-sphenoid ; 15, petrosal ; 17, pre-maxillary; 

 18, maxillary ; 19, dentary and articular elements of mandible ; 20, hyo-mandibular ; 21, quadrate ; 22, meta- 

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

 t-u In in ; 29, sub-operculum ; 30, inter-operculwm behind the gill- rakers ; 31, stylo-hyal ; 32, epi-hyal, ccrato- 

 hyal, and basi-hyal : 33, glosso-hyal ; 34, hrauchi-ostegal rays ; 35, bones of the branchial arches ; 36, uro-hyal. 



culum, which is peculiar 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 

 pieces. The outermost is the epi-branchial, the middle piece is the cerato-= 



