THK STRUCTURE OF THE PIKES SKULL. 



16 r 



bends down at the sides, and so enters into the lateral Avails of 

 the cavity for the orbital muscles. The cartilage, however, does 

 not immediately constitute the floor of the skull, or the roof 

 and side walls of the canal for the orbital muscles, seeing that 

 it is coated over, on both its faces, by bony matter, which is con- 

 tinuous with that forming the inner and the outer faces of the 

 bone Pr.O. 



Although there can be no doubt, then, that the cartilaginous 

 lamella in question forms part of the basi-cranial axis, it does 

 not, strictly speaking, form part of the floor of that skull, being 

 shut out therefrom by the extension over it of the ossifications 

 (Pr.O.), towards the middle line. Leaving these ossifications out 

 of consideration, however, it may be said that the free edge of the 

 middle part of the cartilaginous lamella forms the posterior 

 boundary of the fossa for the pituitary body, which dips down, 

 surrounded by membrane, through the centre of the canal for 

 the orbital muscles, and rests upon the concave surface of an 

 elevation of the bone x at P, Fig. QS. Immediately in front of 



Fig. 68. 



$fl. p\.( Y . 



s.va 



-~E.O. 



B.O. 



.^A 



Tc. 



Fig. 68.— Longitudinal and vertical section of a fresh Pike's skull. The cut surface ot 

 cartilage is dotted. For S. V.G., P. V.G., read a.s.c, p.s.c, as in Figs. 66 and 67. 



this elevation cartilage reappears, and extends, as an inter- 

 orbital, ethmoidal, and internasal septum, to the end of the 

 snout. The cranial cavity rapidly narrows above the cartila- 

 ginous inter-orbital septum, and ends where the olfactory lobes 

 abut against the olfactory sacs. It appears to terminate much 

 sooner, however ; for the olfactory lobes, after running parallel 

 with one another for some distance, diverge, and become sepa- 



