126 



THE SKULL OF MARSUITALS 



It 



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

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



As to skeletal characters, the ilarsupial 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 I'rofessor 

 Parker — to the Schizogna- 

 thous palate of the l)ird. 

 The mandible is inflected ; 

 this familiar character of 

 the Marsupials goes hack 

 to the earliest representa- 

 tives of the order in ileso- 

 -prrsph zoic times (see p. 9G); but 

 it is not absolutely uni- 

 versal, being absent from 

 the much weakened skull 

 of Tursi'pes. On the other 

 hand, the inflection is nearly 

 as great in certain Insecti- 

 vores, in Otocyon, etc. The 

 malar always extends liack 

 to form part of the glenoid 

 cavity. The shoulder girdle 

 has lost the large coracoid 

 of ]\lonotremes ; tlus bone 

 has the vestigial character 

 that it possesses in other 

 Eutheria. The clavicle is 

 present except in the Teranielidae. 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 I'dramehs removes one reason for regardinu- 



bas.oc 



I'lu. 62. - Skull of Rock Wallaby [Petrngale 

 periiciUata). (Ventral view.) »/(', Alisplieuoid; 

 has.iir, basi-occipital ; bas.sjA, basi-.spheuoid ; 

 ex.nc, e.x-occipital ; jw, jugal ; ma.r, maxilla ; 

 pal, palatine ; yar.oc, i)aroeeiiiital ; pjut'.':, 

 premaxilla ; /ir.S2Jli, pre.spliKnoid ; pt, ptery- 

 goid ; sq. .squamosal ; ti/, tympanic. (From 

 Parker and Haswell's Znohiijij.) 



