64 PROFESSOR OWEN ON THE GENUS DINORNIS. 



This appears to be of the same species as the more mutilated cranium figured in 

 vol. iii. pi. 55. figs. 4 & 5. 



The paroccipitals (4) are less e.xpanded relatively than in the Pal. ingens, and are 

 almost straight vertical plates. 



The apophysary part of the mastoid (s) is also vertical, straight, and compressed from 

 behind forwards with the outer border a little advanced. 



Between this and the [lostfrontal intervenes a wide and deep temporal fossa, much 

 exceeding in its proportional size that of the Palapteryx figured in pi. 54. fig. 1. 



The postfrontal {12) is long, three-sided, and curves outwards, downwards and back- 

 wards as low down as the mastoid. 



The pterapophyses (5') are shorter than in the Ostrich or Emeu, and are depressed. 

 The base of the alisphenoid swells out a little above them. 



The cranium, PI. XXIV. fig. 5, is somewhat smaller than that of the Palapteryx figured 

 in vol. iii. pi. 54 ; it more nearly corresponds in size with that figured in vol. iii. pi. 55. 

 fig. 3, but it differs in the greater elevation of the frontal region, which is more marked 

 than in any skull of Dinornis or Palapteryx I have yet seen. This skull is of a mature 

 bird : all the cranial sutures are obliterated ; and we learn from the specimen of the 

 young Dinornis, PI. XXIV. fig. 2, that, as in the Ostrich, this obliteration did not take 

 place in these wingless birds until they had nearly arrived at their full size. 



The interorbital part of the skull is relatively narrower than in the Palapteryx (vol. iii. 

 pi. 54) : the temporal fossae are relatively narrower than in the skull, PI. XXIV. fig. 6. 



The occipital condyle is more sessile than in the larger species, and the occipital 

 foramen is less vertical, the plane sloping from above downwards and a little forwards. 

 The mastoid is shorter and more pointed, and the pneumatic hole is reduced to a very 

 small foramen behind its base. 



The interorbital septum is entire and thick ; a slender compressed process (PI. XXIV. 

 fig. 5, 14) is sent down from it just behind the large olfactory fossa. The cranial end of 

 the premaxillary, which is bifid as in the Ostrich, has coalesced with the frontal; but 

 they remain distinct from the subjacent prefrontals, which have as usual coalesced 

 together to form the cavities for the olfactory capsules. The septum between these 

 cavities is entire. 



The skull, of which a vertical section is figured in PI. XXIV. fig. 4, appears to belong to 

 the same species as that figured in vol. iii. pi. 55. fig. 5, and differs from those figured in 

 PI. XXIV. figs. 5 & 6 in the minor development of the mastoid and postfrontal processes. 

 The olfactory chambers (is) are deep, and the diameter of the single orifice penetrating 

 the upper and back part of the roof of each division of that cavity, indicates the large 

 size of the olfactory nerve. The outer and inner tables of the cranium are seen to be 

 divided by a diploe of air-cells about one and a half line thick ; but the extent of the 

 diploe varies much when seen in transverse section. 



The epencephalic chamber [a, v, c) is remarkable for its size, rising to the highest level 



