182 PROFESSOR OWEN ON THE GENUS DINORNIS. 



form of cranium. In the smaller species of Binornis, 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 Apteryx still further than the 

 cranium from the character of the skull in Dinornis. 



The 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 tympanies, 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 vomer and 

 pterygoids ; so that the upper beak, as a single bone, articulates with the tympanies 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 tympanies 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 1). maximus, 

 I subjoin a figure of the base of the skull in the smaller Moa (Plate XXXI. fig. 1) ; it 

 closely repeats tlie characters shown in D. ingens ^ 



In Dinornis crassus the palatal plates of the palatines (ib. :;o) are anterior horizontal 

 expansions 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 maxiUo-palatine part of that roof, including 

 parts of both bones. In the skull of Dinornis ingens, figured in pi. 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 D. 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. o'assus, as in D. ingens and D. maicimus, 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. 80c. vol. vii. jjlate sv. fig. 3. - Ib. p. 1:^3. 



