132 PROFESSOR OWEN ON THE GENUS DINORNIS. 
a narrower base, in D. robustus (Trans. Zool. Soc. vol. v. pl. 54. fig. 2,4). The ptery- 
goid and pterapophysial (pt) articular surfaces are well marked. 
The mandible (Pl. XI. fig. 1, 29, and figs. 7, 8,9), nearly 5 inches in length, has a more 
irregular upper border than in most Moas, owing to the deeper emargination between 
the coronoid process of the surangular (29') and the alveolar border of the dentary (32’). 
The posterior triangular fossa is deeper and better-defined than in Dinornis elephantopus ; 
its upper and outer angle is more produced; the expanded articular part is longer in 
proportion to its breadth. But the chief and most recognizable modification is at the 
rostral or symphysial end (figs. 8, 9), which is more expanded, more obtuse, and 
shallower above (fig. 9) than in D. elephantopus—conforming in shape to that of the 
premaxillary. 
Skull of Dinornis rheides, Ow. (Plate XII.) 
With the sternum and limb-bones of Dinornis rheides, in the collection of H. Sumpter, 
Esq., of which the former bone was described in Memoir No. XIII., there was a 
cranium and mandible proportionate in size. In the collection of Moa-remains 
brought by Mr. Walter Mantell from Ruamoa there were, with limb-bone evidences of 
Dinornis rheides, two skulls, more or less entire, which so clearly agree with that above- 
mentioned that I refer them to the same species; and this species I believe, on this 
evidence, to be D. rheides. 
The cranium is narrower in proportion to its length than in D. crassus. ‘The super- 
occipital so projects at its midpart as to- conceal the condyle from view, looking 
directly upon the calvarium: comp. Pl. XII. fig. 3, with pl. 53. fig. 1 (Vol. V.), D. robustus. 
From this structure the plane of the occipital foramen (Pl. XII. fig. 2, m) is less vertical, 
inclining from above downward and a little forward to the condyle. From the pro- 
minent upper border of the foramen the superoccipital plane inclines from below, 
upward and forward, at an angle of 50° with the basi-presphenoidal axis. If the 
occipital plane be understood as the hind wall or face of the skull from the basioccipital 
mammille (ib. 1’) to the superoccipital crest (ib. 3), such plane lies nearly at a right angle 
with the basi-presphenoidal axis. But in the present and some other dinornithine 
skulls it describes a convex curve vertically, of which the upper border of the foramen 
magnum is the most prominent part (ib. fig. 1,437). The basicranial axis is usually 
understood to traverse the lower border of the occipital foramen, and it would then be 
out of the parallel of that of the basi-presphenoidal tract or axis'. 
The occipital condyle forms rather more than half a hemisphere, truncate above, from 
the mid part of which a slight depression or dimple extends toward the middle of the 
condyle. The crenate ridge (3) and the more advanced upper transverse superoccipital 
» What Mr. Parker may mean by the “ occipital plane,” which he says “lies nearly at a right angle with the 
basicranial axis in the typical bird” (Zool. Trans. yol. y. part 3, p. 156), is as uncertain and as conjectural as 
that bird itself. 
