154 



THE ANATOMY OP VERTEBEATED ANIMALS. 



sagittal swtiire, as in most of the higher Vertebrata, but are 

 very generally separated by the junction of the frcmtals with 

 the supra-occipital. 



2. The large frontals {Fr.), which may or may not tmite 

 into one. 



3. The nasal bones (Na.), apparently replaced in the Pike 

 by the bones 1 and 2. 



f^: so-mo. 



Fig. a6. — Side and upper views of the skull of a Pike {jEsox lucius), 

 without the facial or supra-orbital bones: — y, the basisphenoid ; 

 z, the alisphenoid ; a, the articular facet for the hj'omandibular 

 bone. 



The under-surface of the skull possesses two membrane 

 bones : in front the vomer (Vo.), and, behind, the huge para- 

 sphenoid (x, x), which ensheathes all the basis cranii, from 

 the basi-occipital to the vomer. 



A supra-orbital bone [S.Or.) is the only membrane bone 

 attached to the sides of the brain-case. Two premaxillary 

 bones (Pmx.) are attached, sometimes closely, sometimes 

 loosely, to the anterior extremity of the cranium; and behind 

 these are the maxillae {Mx.), which are sometimes large and 

 single, as in the Cyprinoid fishes, but may become subdivided, 

 or be reduced to mere styliform supports for cirri, as in 

 many Siluroid fishes. In most osseous fishes the maxillae 



