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IX. On Dinornis (Part XVI.): containing notices of the Internal Organs of some species, 
with a description of the Brain and some Nerves and Muscles of the Head of' the 
Apteryx australis. By Professor Owen, .R.S., F.ZS8., &e. 
Read May 26th, 1870. 
[Puates XLV. to XLVII.} 
§ 1. Introduction. 
] AVAILED myself of the section of the mutilated cranium of Dinornis giganteus, 
described and figured in Part XIV.', to take a cast of the cavity (Pl. XLV. figs. 11, 
12, 13), which affords an instructive representation of the brain of that species. 
As my papers on the bones of Dinornis were preceded by a description of the osteology 
and myology of Apteryx,so I propose now to communicate some notes and figures made 
in the year 1848 from dissections of the brain and certain nerves of the head of the 
Apteryx australis, which I have kept back until I have been able to get satisfactory 
evidence of the brain of the Dinornis, with a view to bringing out the characteristics 
of which my investigations of that organ in the small surviving representative of the 
gigantic Dinornithide of New Zealand were mainly conducted. 
§ 2. Brain of Apteryx. 
The brain of the Apteryx australis (Pl. XLV. figs. 1-10) is of an ovate subdepressed 
form, 14 inch in length, 1 inch 3 lines in breadth; the cerebral hemispheres (a) overlap 
the optic lobes and four-fifths of the cerebellum (c); they are defined anteriorly from the 
olfactory lobes (fig. 2, 7) by a curved linear depression (a'), convex forward. 
Thus, as in most Mammals, three of the primary cerebral vesicles, or divisions of the 
brain, are exposed by removal of the calvarium, whilst no part of the mesencephalon 
comes into view. 
At the base of the brain (ib. fig. 3) the myelon (m) expands into a long macro- 
myelon (d). This shows on each side the small pneumogastric swelling (v), and the 
larger trigeminal one (¢r); it then expands vertically, as well as laterally, at d, for the 
grey centres in connexion with the “ crura cerebri” (fig. 4, /), the smaller fascicules 
diverging to the cerebellum and the mesencephalon. The length of the macromyelon 
(“ oblong medulla” of Anthropotomy) is half an inch, its extreme breadth 4 lines; the 
under surface is impressed by a median line or furrow for the basilar artery (fig. 3, e), 
which is formed, as in birds generally, by the two “arteriz communicantes” (f) sent 
Trans. Zool. Soc. vol. vii. p. 138, pl. 13. fig. 9. 
VOL. VIIL—PART V. January, 1871. 3G 
