214 'THE SKULL. [chap. 



is flattened from above downwards, and inclined consider- 

 ably inwards. 



The hyoid (Fig. 67) 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, imperfectly ossified ceratohyals {ch)., partially 

 ankylosed to the basihyal, and without any other ossifica- 

 tions in the anterior cornua. The thyrohyals (///) are tole- 

 rably long, flattened bars, meeting in the middle line at their 



Fig. 67. — Upper surface of hyoid of Thylacine (nat. size), bh basihyal ; ch ceratohyal 

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



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 

 diff"er in general appearance from that of the Thylacine, 

 agree with it in the following important particulars : — 



I. The brain cavity is small, with the cerebellar fossa 

 entirely behind, and the olfactory fossa entirely in front 

 of the cerebral fossa. There are, however, degrees in 

 this respect, the Kangaroos representing one extreme, with 



