58 



THE AMERICAN NATURALIST. [Vol. XXXVII. 



"The elevated body of the premaxilla with its distinct pre- 

 narial septum in Casuarius. 



"Forbes's discovery {Trans. Nat. Zodl. Inst.,W6i. XXIV, 1891, 

 p. 185) of a dinornithine bird which he calls Palaeocasuarinus 

 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 tibiae upon which the genus 

 is founded have, as the name implies, a remarkable resem- 

 blance to those of the cassowary. 



" On the other hand, I know of no character in the skull of 

 Rhea by which it definitely approaches the moas, and the 

 presence of a maxillary process to the nasal, the form of the 

 cerebral fossae, and the position of the pneumatic foramen of 

 the quadrate seem the only particulars in which the ostrich 

 comes in any way near them. Struthio and Rhea are, in fact, 

 sharply separated both from one another and from the Austral- 

 asian Ratitae, 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 Ratitae are of two kinds : ancestral 

 characters, such as the form of the vomer, the basipterygoid 

 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-Carinatae ; 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 the 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 



