A character of the brain of Marsupials has been the subject of some controversy. Sir Richard Owen stated many years ago that they were to be distinguished from the higher mammals by the absence of the corpus callosum. Later still it was urged that a true corpus callosum, though a small one, was present; while, finally, Professor Symington[71] seems to have shown that {126} 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 presphenoid. The palate is largely fenestrated, a return as it were--says Professor Parker--to the Schizognathous palate of the bird. The mandible is inflected; this familiar character of the Marsupials goes back to the earliest representatives of the order in Mesozoic times (see p. 96); but it is not absolutely universal, being absent from the much weakened skull of _Tarsipes_. On the other hand, the inflection is nearly as great in certain Insectivores, in _Otocyon_, etc. The malar always extends back to form part of the glenoid cavity. The shoulder girdle has lost the large coracoid of Monotremes; this bone has the vestigial character that it possesses in other Eutheria. The clavicle is present except in the Peramelidae. A third trochanter upon the femur seems to be never present. [Illustration] FIG. 62.--Skull of Rock Wallaby (_Petrogale penicillata_). (Ventral view.) _ali_, Alisphenoid; _bas.oc_, basi-occipital; _bas.sph_, basi-sphenoid; _ex.oc_, ex-occipital; _ju_, jugal; _max_, maxilla; _pal_, palatine; _par.oc_, paroccipital; _p.max_, premaxilla; _pr.sph_, presphenoid; _pt_, pterygoid; _sq_, squamosal; _ty_, tympanic. (From Parker and Haswell's _Zoology_.)