164 



ON THE STRUCTURE OF THE SKULL. 



nected an upper arch, forming part of the brain-case, and 

 a lower arch which enters into the composition of the face. 

 The sides of this arch in the sectional view are partly constituted 

 (compare Fig. 48) by bones specially connected with the audi- 

 tory apparatus, and the peduncle of the lower arch is articulated 

 with these bones. The chamber contained within the lower 

 arch, however, differs from that seen in the section of the 

 human skull in that it is entirely devoted to the buccal cavity, 

 and is not subdivided by processes of the palatine and maxillary 

 bones into an upper, nasal, and a lower, oral, passage. 



Fig. 6G. 



EpQjif.c . S.p J is.o. Efi-O. 



KM 



Fig. 66. — The posterior segment of the skull of a Pike which has been vertically and 

 transversely bisected. The bones of the inferior arch are represented diagrammati- 

 eally. The epiotic, opisthotic, pro-otic, and squamosal bones are left unshaded, as in 

 the corresponding section of the human skull, p.s.c, e.s.c, arrows indicating the 

 positions of the posterior and external semicircular canals; x, parasphenoid. 



The comparison of the transverse sections of the Pike's with 

 those of the Man's skull thus enables us to perceive certain 

 resemblances between the two. In each there is an axis, upper 

 and lower arches ; in each the section separates the bones which 

 lodge the auditory organs ; and the most apparent difference 

 between the two is the vastly greater proportionate size of the 

 periotic bones in the Tike. 



