238 THE SKULL. [CHAP. 



and not perforated, the optic nerve passing out through the 

 sphenoid al fissure. 



The ascending ramus of the mandible is less elevated than 

 that of the Dog, the condyle being almost on the same level 

 as the molar teeth. The coronoid process has a more back- 

 ward inclination. The masseteric fossa has a powerful, 

 externally projecting lower border, and the angular process 

 is flattened from above downwards, and inclined consider- 

 ably inwards. 



The hyoid (Fig. 71) is constructed on a totally different 

 type from that of the Dog. It consists of a small flat lozenge- 

 shaped basihyal (bh\ surmounted by flattened, triangular, 



C/l 



FIG. 71. Upper surface of hyoid of Thylacine (nat. size), bh basihyal ; ch ceratohyal 

 (anterior cornu) ; th thyrohyal (posterior cornu). 



imperfectly ossified ceratohyals (ch\ partially ankylosed to 

 the basihyal, and without any other ossifications in the 

 anterior cornua. The thyrohyals (th) are tolerably long 

 flattened bars, meeting in the middle line at their attachment 

 to the basihyal, and with their free, or laryngeal, extremities 

 expanded, but still cartilaginous in the perfectly adult animal 

 from which the above figure was taken. 



All the other animals of the sub -class which contains the 

 single order Marsupialia, however their skulls may differ in 



