i4 



CEREBRAL DEVELOPMENT 



On each side of this external cranium, the various cerebral 

 plates, like the corresponding cerebral ribs in the osseous 

 fishes, were free, at least not anchylosed together ; and some 

 of their number unequivocally performed, in part at least, 

 the functions of two of these cerebral ribs, viz., the upper 

 and under jaws, with those of the opercular appendages 

 attached to the latter. In the cod, as in most other osse- 

 ous fishes, the upper portion of the cranium consists of thir- 

 teen bones, which represent, however, only seven bones iu 

 the human skull, — the nasal, the frontal, the two parietal, 

 Fig. 10. 



a a 



UPPER SURFACE OF CRANIUM OF COD. 



A, Occipital hone. 



B, B, Parietals. 



C, C, C, Superior frontal. 

 I, Nasal hone. 



D, D, Anterior frontal. 



F, F, Posterior frontals. 

 E, E, Mastoid hones. 

 2, 2, Eye-orhits. 

 a, a, Par-occipital hones. 



* Professor Owen, in fixing the homologues of the ichthyic head, 

 differs considerably from Cuvier ; but his view seems to be the cor- 

 rect one. It will, however, be seen, that in my attempted compari- 



