176 ON THE STRUCTURE OF THE SKULL. 



The principal bones which surround the oral cavity in the 

 Pike are disposed, as in Man, in pairs, some being in front of 

 and above the oral aperture, while others are behind and below 

 that aperture; and they inclose the buccal and pharyngeal 

 chambers. 



Fig. 71. 



KM. / 



Fjcr. 71. — Palato-quadrate arch, with the hyomandibnlar and symplectic, the articular 

 piece of the lower jaw, and Meckel's cartilage, of the Pike, seen from the inner side. 

 a, the cartilage interposed between the hyomandibnlar and the symplectic; b, that 

 which serves as a pedicle for the pterygopalatine arch ; c, process of the hyoman- 

 dibular with which the operculum articulates ; d, head of the hyomandibular which 

 articulates with the side of the skull. 



The anterior pair of pre-oral bones (Pmx. Fig. 65), small, and 

 beset with teeth upon their under-surfaces, are connected with the 

 vomer and the termination of the cartilaginous rostrum formed 

 by the internasal septum. They obviously answer to the human 

 pre-maxillse. An elongated bone (Mx.), which bears no teeth, 

 is connected anteriorly with the pre-m axilla, and, lying external 

 to the other pre-oral bones, forms the boundary of the gape. 

 Its homology with the maxilla of Man appears to be unquestion- 

 able. A second smaller bone is connected with the posterior 

 part of the upper edge of the maxilla, and is usually regarded 

 as a subdivision of it. 



Behind the pre-maxillse, and internal to the maxillae, in the 

 situation occupied by the palatine and pterygoid bones in Man. 

 the Pike has an osseous arch of much greater complexity and 

 somewhat different connections. 



The summit of this " palato-quadrate ' ; arch is moveably 

 articulated, by a cartilaginous pedicle, with the outer surface of 

 the pre-frontal process of the skull. The anterior crus of the 



