THE STRUCTURE OF THE PIKE'S SKULL. 165 



The comparison of the longitudinal section of the Man's 

 skull with that of the Pike (Fig. 68) confirms the conclusions 

 arrived at from the study of the transverse sections. A "cranio- 



Fig. 67. 



» a.s'.c 



Fig. 67. — The anterior segment of the skull represented in Fig. 66. — Mn, mandible. 

 a.s.c, arrow indicating the position of the anterior semicircular canal. The letters 

 B, 8, one on each side of the basi-sphenoid, are seen through the canal for the orbital 

 muscles. The pro-otic bone is left unshaded. In this, and in the preceding figure, 

 the dotted shading indicates cartilage ; but, as the drawings were made from a dry- 

 skull, it must be remembered that the whole of the cartilage entering into the 

 cranium is not represented. 



facial axis," composed partly of bone and partly of cartilage, 

 extends from the occipital foramen to the anterior extremity of 

 the snout of the fish. The posterior part of this constitutes the 

 floor of the cranial cavity, and is the basi-cranial axis. The 

 anterior part, excluded from the cranial cavity, is, as in Man, the 

 basi-facial axis. 



Again, as in Man, three pair of chambers, destined for the 

 lodgment of the organs of the higher senses, are placed sym- 

 metrically upon the sides of the Pike's skull. The olfactory 

 chambers are situated just in front of Prf., in Fig. 65, and the 

 orbits beneath S.Or., while the auditory organs are inclosed 

 within the posterior bony walls of the brain-case, as indicated 

 in the transverse sections. And, as in Man, the olfactory and 



