424 PEOF. T. JEITEET PiEKER ON THE CEANIAL OSTEOLOGT, 



The general relations of the vomer, palatines, and pterygoids in both genera. 



The presence of a vestige of the maxillary process of the nasal in Bromceus. 



The well-ossified antorbital ankylosed to the descending process of the lacrymal in 

 both genera. 



The elevated body of the premaxilla with its distinct prenarial septum in Casuarius. 



Dr. Forbes's discovery (i) of a dinorni thine bird which he calls Palceocasuarinus 

 will, if the detailed account of his very interesting researches bears out the opinions 

 expressed in his preliminary note, lend strong support to this view. The tibise upon 

 which tlie genus is founded have, as the name implies, a remarkable resemblance to 

 those of the Cassowary. 



On the other hand I know of no character in the skull of Bhea by which it defi- 

 nitely approaches the Moas, and the presence of a maxillary process to the nasal, the 

 form of the cerebral fossse, and the position of the pneumatic foramen of the quadrate 

 seem the only particulars in which the Ostrich comes in any way near them. Strutkio 

 and Rhea are, in fact, sharply separated both from one another and from the Australasian 

 Eatitse as well by the characters of the bony palate as by those of the pelvis. The 

 characters possessed by them in common with the other Eatitse are of two kinds : 

 ancestral characters, such as the form of the vomer, the basi-pterygoid processes, and 

 the single-headed quadrate, which, according to the view taken in this paper, are 

 accounted for by the hypothesis of common descent from a group of generalized flying 

 birds or Proto-Carinatse ; and adaptive characters, such as those of the sternum, 

 shoulder-girdle, and wing, which they share to a greater or less degree with all flightless 

 birds. 



The marked differences between the Moas and Kiwis are certainly for the most part 

 adaptive : the two families resemble one another in the increased size of the olfactory 

 organ and the reduced size of the eye ; but both processes have gone so much further in 

 Apteryx that the differences between the two, in this respect alone, give their skulls 

 the appearance of being more widely separated than those of any other two ratite birds. 

 The real affinities underlying these differences are, however, shown by the striking 

 similarity of the bones of the palate in the two forms. The absence of a maxillary 

 antrum in Apteryx seems at first sight a difference of great importance, but the fact 

 that this cavity has disappeared or become vestigial in one of the most specialized 

 genera of Moas seems to indicate that its complete atrophy in the Kiwi is simply to 

 be looked upon as an instance of the extreme specialization of that genus. 



As to the origin of the various genera of Dinornithidse, I am not altogether in accord- 

 ance with Prof. Hutton (9, p. 428). I think there can be no doubt that Dinornis and 

 Emeus have diverged furthest from the ancestral stock, but in opposite directions ; and 

 that the narrow-beaked forms are the most generalized. Of the three narrow-beaked 

 genera, Mesopteryw appears to me to deviate least from the ordinary type of the 

 Eatitse, its comparatively lightly-built skull and slender mandible bringing it nearer 



