PROFESSOR OWEN ON THE GENUS DINORNIS. 65 
of the prosencephalic one (p), and sinking much below it ; the mesencephalic fossa (0) 
is comparatively small. 
The transverse section across the broadest part of the cranium shows that the pros- 
encephalic cavity is far from being of corresponding breadth: a considerable extent 
of diploé intervenes between that chamber and the base of the postfrontal processes. 
The outer and inner tables unite without diploé above the highest part of the upper 
longitudinal elevations of the cerebrum. The inner circumference of the olfactory 
orifices is partially grooved. 
In order to gain some idea of the size of the bird to which the largest cranium 
belongs, I have compared the diameter of its foramen magnum with that of a lower 
cervical vertebra and of a middle dorsal vertebra, both referable by their size to the 
Dinornis giganteus, the same comparisons having previously been made in the skeleton 
of the Ostrich. 
Dinornis. Ostrich. 
Lines. Lines. 
Transverse diameter of the foramen magnum Pe ery As ese e9 65 
Transverse diameter of middle of spinal canal, lower cervical vertebra . 63 5 
Transverse diameter of middle of spinal canal, dorsal vertebra. . . . 7 44 
From the above admeasurements and comparison we might be led to conclude that 
the skull of the Dinornis yielding that of the foramen magnum belonged to a larger 
species than the vertebra ; but the size of these vertebre forbids the supposition ; for 
they are larger in proportion to the size of the skull compared, than in the Ostrich. 
The canal for the spinal chord is, in fact, singularly small in proportion to the bulk of 
the entire vertebra in Dinornis as compared with that in the Ostrich or other birds, 
and forms, as I have pointed out in a former Memoir, one of the peculiarities of the 
large wingless birds of New Zealand. The cervical vertebra, for example, with a spinal 
canal six and a half lines wide, has a body of four inches in length; whilst that of the 
Ostrich with a spinal canal five lines in diameter has a body only two and a quarter 
inches in length ; and the dorsal vertebra presents similar relations. 
Lower jaw.—An almost entire lower jaw of a Dinornis or Palapteryz, of rather smaller 
size than the one of which a large portion is figured in vol. iii. pl. 54. figs. 6, 7, closely 
accords with that portion as far as they can be compared: the symphysial end of the 
jaw is rounded and short, and impressed below by two parallel longitudinal grooves, sg. 
Each ramus is slightly bent in a sigmoid flexure, concave below at the anterior half, con- 
vex at the posterior one. The alveolar border is pierced by vascular grooves and fora- 
mina at its anterior part, and obliquely levelled off to an edge behind. There is on 
coronoid process, and no vacuity in the ramus of the jaw, but only a deep longitudinal 
groove half an inch long, between the originally distinct ‘ angular’ and ‘ surangular’ 
pieces, which groove is completely closed up on the inner side by the splenial piece : 
in this respect the present lower jaw differs from that portion of a very large one 
ascribed to the Dinornis in my former Memoir, vol. iii. pl. 53. figs. 1 & 2. . 
