326 
MEMOIR 
ON THE 
BRAIN, LARYNX, AND TRACHEA 
IN THE 
GENUS DINORNIS. 
§ 1. Brain of Dinornis. 
RETURNING to the brain of the Apteryx, the side view (fig. 1) is contrasted (in 
Pl. XCI.) with that of the Dinornis (fig. 11), the upper view (fig. 2) with fig. 12, and 
the under view (fig. 3) with fig. 13. 
The Dinornis differs in the minor relative size of the cerebrum to the cerebellum, 
which latter (figs. 11 & 12, ¢) rises wholly behind and uncovered by the hemispheres (a). 
The cerebrum appears to be broader, because it is so much shorter, relatively, than 
that of the Apteryx; its upper surface is much more accentuated. A broad and high 
longitudinal tract (a), next the mid line, is divided from the outer part of the hemi- 
spheres ; and this is partially subdivided into a posterior (a) and anterior (a') portion by 
a shallow depression answering to the “Sylvian fissure.” 
The optic lobes (ib. figs. 11, 12, 13, 4, 6) are, relatively as well as absolutely, larger than 
in Aptery#, corresponding with the indications, given by the orbits or bony beds, of the 
larger and better-developed organs of vision in Dinornis, the species of which we may 
conclude to have been diurnal; they are visible in the upper view (ib. fig. 12, 4, b) as 
well as in the side view (ib. fig. 11), 
No demarcation of a “pons” can be satisfactorily traced on the cast; but the tri- 
geminal swelling is plain. The length of the macromyelon is 11 lines, its breadth is 
9 lines. 
The cerebellum shows a pair of low lateral lobes (ib. fig. 11, c’) at its fore part, and 
behind this the depression answering to the upper semicircular canal. The length of 
the cerebellum is 1 inch 2 lines, its breadth at the lateral lobes is 1 inch. The vertical 
diameter of the epencephalon (ib. c, d) is 1 inch 4 lines; the breadth of the mesence- 
phalon (fig. 13, 7, 6), taken outside of the optic lobes, is 1 inch; the length to the fore 
part of the chiasma is 8 lines; each optic nerve (¢) has a thickness of 2 lines. The breadth 
