PROFESSOR OWEN ON THE GENUS DINORNIS. 357 



in the Apteryx, but more resembles the same process in the Emeu. The pneumatic 

 foramen of the tympanic is in the hinder depression between the upper condyles. The 

 chief peculiarity of this bone is the large size, backward extension, and upward curve 

 of the broad inferior condyle (?', i). 



In Didus the tympanic bone is subquadrate with the four angles produced, and the 

 upper and hinder one bifurcate, forming tJie bifid condyle for the mastoid articular cups. 

 The orbital process forming the anterior angle is compressed and truncate ; the outer 

 surface of the bone is smooth and convex vertically ; the inner surface is traversed by 

 a sharp concave ridge extending from the inner division of the upper condyle to the 

 anterior part of the inner and lower condyle : the anterior division of the inner surface 

 is concave ; the posterior one is concave vertically, convex transversely. The antero- 

 posterior extent of the condyle for the lower jaw is little, but greatest at its outer part 

 where it rests upon the shallow reniform outer division of the concave articular part of 

 the lower jaw : the inner more ridge-like part of the condyle sinks into a deeper trans- 

 versely extended depression of the same articular concavity. 



There is no trace of lower jaw belonging to the cranium above-described. The pos- 

 terior portion of a left ramus (PI. LIII. figs. I, 2 & 3) has been articulated to a tym- 

 panic bone of at least double the size of the one in that cranium, and probably belongs 

 to one of the larger species of Dinornis. The anterior portion of the lower jaw (PI. LIV. 

 figs. 6 & 7), though corresponding in size with the cranium of the Dinornis casuarinus, 

 has belonged to a distinct genus of bird, of which the extremity of the premaxillary 

 bone (PI. LIV. figs. 1, 2 & 3, 22), conformable to that anterior end of the mandible, has 

 been fortunately transmitted. There are also three portions of an almost entire lower 

 jaw (PI. LVI. figs. 7s, 12 & 13) belonging to a skull of smaller size than either of the 

 above, and to a bird of a different genus. I shall, therefore, conclude the present 

 section by some general remarks on the skull of which the characters of the constituent 

 bones have been noticed above. 



In the proportions of the cranial or cerebral to the facial or rostral parts, this skull 

 offers the medium or normal character, such as is exemplified in the larger existin"- 

 Struthious birds ; but the beak is stronger, especially deeper, with more uniform breadth, 

 and a greater curve ; it is also broader and flatter at the extremity than even in the 

 Ostrich, and much more so, therefore, than in the Rhea, Emeu or Cassowary : neither 

 has it a median raised portion defined by longitudinal parallel grooves continued back- 

 wards to the external nostrils, as in those Struthionida; and as also in the Apteryx. The 

 cranial portion of the skull is remarkable for the great breadth and depth of its occipital 

 region, and for the strength of the ridges, tuberosities and processes by which that region 

 is defined. No known existing bird can compare with the Dinornis in this respect, or 

 in the very singular downward development of the massive wedge-shaped basioccipito- 

 sphenoidal part of the cranium (see fig. 4, PI. 52). The cranium decreases in depth 

 towards its anterior boundary, but comparatively little in breadth, until anterior to the 



