56 Zoological Society. 



cence with the alisphenoids behind, the frontals above, the prefrontals 

 in front, and the presphenoid below : they send a ridge upwards and 

 outwards to the under part of the postfrontals, but do not present 

 that singularly swollen character which is so peculiar in Didus ; in 

 which also the prefrontals form a large smooth protuberance, like a 

 tumour, at the fore-part of the orbits, and appear on the upper sur- 

 face of the cranium in front of the antorbital process of the true frontal 

 and external to the lachrymal. The interorbital bony septum is entire 

 in both Dinornis and Didus ; but in the latter it is more than an 

 inch in thickness and cellular, and in this respect more resembles 

 the singular structure of the part in Apteryx. The orbits are smaller 

 in Dinornis than in the large existing Struthionidce or in Otis, but 

 are larger than in Apteryx. The olfactory chambers in Dinornis are 

 less developed than in Palapteryx and Apteryx. 



The nasal bones in Dinornis and Otis converge where they over- 

 lap the prefrontal (ethmoide, Cuv.) in order to join the frontal and 

 include that end of the nasal process of the premaxillary, which is 

 on a lower plane ; and, as they advance, they pass beneath that 

 process, coalesce with it and with each other, and terminate in 

 Dinornis in a point. In Didus the nasals also anchylose with the 

 frontal, where they are separated by the nasal process of the pre- 

 maxillary, as indicated by the two longitudinal fissures, which, com- 

 mencing behind at 2 lines distance from the outer border of the 

 anchylosed base of the beak, gain that border at 1 inch 9 lines 

 distance from the frontal, and thus indicate the proportions of the 

 base formed by the anchylosed nasals : the fissure can also be traced 

 as in Dinornis, bending inwards upon the under surface of the nasal 

 process of premaxillary, to about 3 inches from the frontal, when 

 the fissure returns back, inclining to the median line, and meets its 

 fellow there. All the outer part of the median stem or base of the 

 beak defined by these linear furrows I regard as the nasals, which 

 thus support the nasal process of the premaxillary. 



This process is a broad transversely arched plate, where it joins 

 the maxillary processes to form the anterior or rostral part of the 

 premaxillary ; the extent of which, anterior to the external nostrils, 

 is 2^ inches, the whole length of the premaxillary being 4-^ inches. 

 Its breadth at the middle is rather more than an inch ; the depth of 

 the upper bony beak gradually decreases from its base where it is 

 1 inch 9 lines, to its apex where it is less than 1 line, but retains 

 a breadth of 8 lines, the edge appearing to have been truncate or 

 very slightly rounded off : the whole upper beak being gently arched 

 to this terminal edge resembles the cooper's adze {doloire, Fr.). 

 The palatal surface is broad, very slightly excavated, and bounded 

 laterally by well-defined alveolar ridges : the palatal nostril com- 

 mences anteriorly 1 inch 10 lines from the anterior border of the 

 premaxillary. In Didus the nasal process of the premaxillary pre- 

 sents an elliptic transverse section where it quits the maxillary pro- 

 cesses, and diminishes in depth as it retrogrades, becoming depressed 

 and broad where it rests upon and divides the nasals to anchylose 

 with the frontal. Where the nasal and maxillary processes diverge, 



