274 
auswering to the “ maxillary” one or “antrum ”'in Mammals, with a small subtriangular 
aperture posteriorly, which looks backward and downward: the longest diameter of 
this aperture is 4 lines; the sinus is elsewhere closed: its length is 1 inch 2 lines, its 
height 8 lines, and its breadth the same, The inner wall deyelopes a slightly arched 
ridge, which abuts upon the presphenoid below the rhinal plate or “ shelf” (fig. 4, 9”). 
The outer side or wall of the antrum is impressed lengthwise by the termination of 
the alveolar branch of the premaxillary (fig, 1, 22"): the palatal plate of the maxillary, 
forming the floor of the antrum, is underlapped anteriorly by the palatal plate of the 
premaxillary, and abuts by its median margin upon the fore part of the yvomer. The 
maxillary or descending branch of the nasal, with the contiguous part of the rhinal cap- 
sule, articulates with the outer and back part of the antrum. Below this, and external 
to the antral orifice, the maxillary contracts to the slender subtrihedral bar passing 
backward and outward to coalesce with the slender malar (fig. 1, 26), The under facet of 
the maxillary is impressed with the backward prolongation of the alveolar channel. 
Thus the maxillary manifests its true nature and homology with the bone so called in 
the Mammal, in the clearest and most unmistakable manner in Linornis. In all birds 
it retains the more essential and constant characters of 21 in Mammals and Reptiles. 
It continues backward the roof of the mouth from the premaxillary palatal process ; 
it continues backward the alveolar process or border, from that grooved border of the 
premaxillary; it sends off the zygomatic process, to which the malar articulates, such 
part of this malar, prior to anchylosis, being overlapped, as is usual, by the maxillary, 
as the malar itself is overlapped by the zygomatic part of the squamosal. 
Accordingly our great masters in Comparative Osteology (Cuyrer®, MEcKEL, GEOFFROY 
S?.-Hinairn) have unhesitatingly recognized the nature of this bone, which only one 
prone to mystify what is clear, and to complicate what is simple and plain, could haye 
persuaded himself to contradict by “vicarious” fancies*, The usual extreme ornithie 
modification of the bone is manifested in D. rheides as in D. robustus (Pl. LXV. 
fig. 1, 2121’), The malar (26), with which it has coalesced, is remarkable in D. rheides 
(at least I have not found the character in the larger dinornithic crania with the 
‘ The corresponding part of the maxillary is described in Dinornis robustus as “ an oblong, bony, pneumatic 
capsule, 2 inches in length and 1 inch 3 lines in breadth, flattened below,” &c. (ante, p. 156). 
* “ Los jugal réunit, comme dans les mammiféres, les parties latérales du crane 4 la faee, par le temporo- 
articulaire [my “sqnamosal’’], et le sus-maxillaire se Joint a ces deux os par une articulation serrée, qui les 
force de suivre ses mouvements en ayant et en arriére. Les os palatins ont une articulation 4 peu prés fixe ou 
trés-mobile avec les 08 sus-maxillaires,” &¢. (Lecons d’Anat, Comp. ed. 1835, tom. iv. p. 112). Cuvier’s « sus- 
maxillaire” is my * maxillary”; his “sous-maxillaire” I call « mandible.” | 
* The “maxillary” is, or rather was, the “prevomer” of Parker, who calls it “ the splint-bone which is vicarious 
of the maxillary in the Bird-class” (Trans. Zool. Soc. vol. v. p. 233), His rectification of opinion (Trans. Zool. 
Soe. vol. viv Ps 502) is based on a distinct ground for the acceptance of homology, viz. “ authority.” It is in 
his case a praiseworthy ground, and needs only a choice of the proper one to lead him to a true view of other 
particulars of the osteology of birds in which he has gone astray, 
