126 



THE SKULL OF MARSUPIALS 



.p.maac 



the original statement of Owen was correct, at least in part. It 



is at most feebly developed (see Fig. 58, p. 118). 



As to skeletal characters, the Marsupial skull has on the 



whole a tendency towards a permanent separation of bones 



usually firmly ankylosed. Thus the orbitosphenoids remain 



distinct from the pre- 

 sphenoid. The palate is 

 largely fenestrated, a return 

 as it were says Professor 

 Parker to the Schizogna- 

 thous palate of the bird. 

 The mandible is inflected ; 

 this familiar character of 

 the Marsupials goes back 

 to the earliest representa- 

 tives of the order in Meso- 

 zoic times (see p. 96); but 

 it is not absolutely uni- 

 versal, being absent from 

 the much weakened skull 

 of Tarsipes. On the other 

 hand, the inflection is nearly 

 as great in certain Insecti- 

 vores, in Otocyon, etc. The 

 malar always extends back 

 to form part of the glenoid 



FIG. 62. -Skull _of Rock Wallaby ' (P^ogale cayit The shoulder gir dle 

 penicillata). (Ventral view.) all, Alisphenoid; * 



bas.oc, basi-occipital ; bas.sph, basi- sphenoid ; has lost the large COraCoid 



2Z-2&?%,% S Z?^ of Monotremes; this boue 



premaxilla ; pr.sph, presphenoid ; pt, ptery- has the vestigial character 

 eoid ; sq. squamosal ; ty. tympanic. (From . i . ,\ 



Parlor and Haswell's /oology.) that lt; POSSCSSeS 111 other 



Eutheria. The clavicle is 



present except in the Peranielidae. A third trochanter upon 

 the femur seems to be never present. 



The Marsupials cannot be regarded as an intermediate stage 

 in the origin of the Eutheria for a number of reasons. In the 

 first place, the nature of their teeth shows them to be degenerate 

 animals ; one set, whether we regard it as the milk or permanent 

 dentition, has become vestigial. The recent discovery of a true 

 allantoic placenta in Perameles removes one reason for regarding 



bas.oc 



