182 PROFESSOR OWEN ON THE GENUS DINORNIS. 
form of cranium. In the smaller species of Dinornis, through the minor difference in 
the size of brain, its case is in them relatively more convex and raised, a character 
which is most marked in the comparatively diminutive Apteryx. As the parts 
furthest from the centre are most subject to modifying influences, the bony framework of 
the beak, of which the palate forms part, departs in Apterya still further than the 
cranium from the character of the skull in Dinornis. 
‘Lhe palatal generic characters of Apteryx are detailed in the second volume of the 
Zoological Transactions, 4to, p. 285, and illustrated in plate vii. fig. 2. The repeated 
pressure to which the beak is subject in perforating the soil for food being transferred 
to the hind buttress-bone formed by the tympanics, all the beak-bones articulated 
therewith have coalesced—the maxillaries laterally with the malo-squamosal styles, and 
mesially with the palatines, these carrying on the coalescence with the yomer and 
pterygoids; so that the upper beak, as a single bone, articulates with the tympanics by 
the diverging columns of its quadrifid base, the two outer and more slender ones with 
the outer cups, the two inner and thicker ones with the inner cups, the latter being 
strongly wedged, moreover, before reaching those latter cups, between the orbital plates 
of the tympanic and the pterapophyses or ‘ transverse processes of the sphenoid.’ The 
advantage of a certain yielding movement of the tympanics under extreme pressure 
cannot fail to be noticed. 
As the dinornithic modifications of the palate are more perfectly demonstrated in the 
skull of a Dinornis crassus, recently transmitted to me, than in that of D. mazimus, 
I subjoin a figure of the base of the skull in the smaller Moa (Plate XXXI. fig. 1) ; it 
closely repeats the characters shown in D. ingens}. 
In Dinornis crassus the palatal plates of the palatines (ib. 20) are anterior horizontal 
expausions of those bones which coalesce with the corresponding palatal plates of the 
maxillaries, not passing beneath them. The bony palate behind the premaxillary part 
of the mouth-roof may be truly termed the maxillo-palatine part of that roof, including 
parts of both bones. In the skull of Dinornis ingens, tigured in pl. xv. fig. 3 of my 
fourteenth part”, a portion of the suture still remains, and a smaller portion is traceable 
in the present specimen of D. crassus. 
Birds have the maxillary, 21, and palatine bones, 20, ossified, as in mammals, from 
separate centres, but have no maxillo-palatine bone, save by the accident of partial 
confluence. ‘The specific palatal distinction from ). ingens appears in the course of the 
suture of the maxillo-palatine plate with the premaxillary. In D. ingens the suture 
runs across in an irregular wavy line; in D. crassus it presents an angular form, the 
maxillo-palatine plate being notched to receive the angular palatine process, 22, of the 
premaxillary. 
In D. crassus, as in D. ingens and D. maximus, the slender part of the palatine, con- 
tinued backward from the palato-maxillary plate, is twisted so as to bring the inner edge 
' Trans. Zool. Soc. vol. yii. plate xy. fig. 3. > Tb. p. 123. 
