126 



COMPARATIVE ANATOMY 



Apart from a median cartilaginous bridge connecting : the 

 anterior orbital region with the nasal capsules, and corresponding 

 to the interorbital septum of the Sauropsida (by the ossification of 

 which a presphenoid may arise), these capsules are connected 



Premax. 



Nasal 

 ... Max. 



Jugal 



Frontal 



Spheneth. cart 



Septum nasi. 

 Orbitonas. Jissure 

 Ala orbital is. 

 Ala temp. 



Sup. orb. Jissure 

 Carotid for. 



Parietal 



Int. aud. ineatut 

 Jug. for. 



Endolympk. for. 



Hypoglossal for 



Tect. synot. 



FIG. 91, A. SKULL OF AN EMBRYO MOLE (42-3 MM. ix LENGTH FROM NOSE TO 

 BASE OF TAIL). FROM AN ENLARGED MODEL, x ^. A, dorsal, and B, ventral 

 view. The investing bones are removed on the left side. (After E. Fischer.) 



with the cerebral part of the chondrocranium merely by thin bars 

 on either side (sphenethmoid cartilage) : the Mammalian skull is 

 therefore of the tropibasic type 1 (p. 77). 



The anterior part of the basis cranii is formed by the ossifica- 

 tion of the' cartilage, which either gives rise to a distinct pre- 



1 Certain facts in the development of the skull in Apes indicate that the 

 Primates diverged very early__irom the common mammalian stem, many primi- 

 tive characters being present which are no longer recognisable in other "lower" 

 Mammals. 



