P. N. Bose—History of the Extinct Carnivora. 277 
was comparatively small. The structure of the brain in the great 
majority of them, as made out from casts either natural or artificial, 
resents some singular points of departure from the typical Carnivora. 
n Arctocyon primevus, according to Prof. Gervais,' the cerebellum is 
completely exposed; the cerebral hemispheres are proportionately 
very small; the olfactory lobes are very well developed, thicker 
than the anterior part of the cerebral hemispheres, and proportion- 
ately longer than in any normal Carnivore. It is only with the 
Marsupials, remarks the learned anatomist, that the brain of the 
Arctocyon could be compared. The brain of Proviverra is not much 
more highly organized; and this is what chiefly reveals to M. 
Gaudry its Marsupial affinities. But I have only to quote the 
following from Prof. Huxley’s description of the brain of such a 
familiar Insectivore as the Hedgehog, in order to show that the low 
type of brain in Arctocyon, Proviverra, etc., has a parallel also 
amongst the Placentals :— 
“The brain of the Hedgehog is remarkable for its low organiza- 
tion. The olfactory lobes are singularly large and are wholly un- 
covered by the cerebral hemispheres ; which, on the other hand, do 
not extend back sufficiently far to hide any part of the cerebellum. 
Indeed they hardly cover the corpora quadrigemina. Only a shallow 
longitudinal sulcus marks the upper and outer surface of each 
hemisphere.” § 
The brain of the Myenodon is much more highly organized, and 
approaches the condition met with in the higher Carnivora, such as 
the Felide.* This confirms in a remarkable manner the conclusion 
to which I was led at the end of the last section, viz. that Hyenodon 
was the most differentiated form in the peculiar group of Carnivores, 
the first link of which as yet known to us is Proviverra. 
The only important points in the osteology of the skull of Are- 
tocyon which have been supposed to indicate its Marsupial connexion 
are the lateral expansion of the zygomatic arches, and the pre- 
sence of a pair of foramina in the hinder portion of the palate noticed 
by Prof. Gervais. The zygomatic arches are not proportionately 
wider in Arctocyon than in the Hedgehog; and the palatal vacuities, 
which would seem to have afforded Gervais and Gaudry incontro- 
vertible evidence of the Marsupiality of Arctocyon, are by no means 
uncommon among the Insectivores (e.g. Tupaia, Erinaceus, etc.) 
Vacuities in the pusterior portion of the palate have not been 
detected in any other Eocene Carnivore. All the genera (Hyenodon, 
Pterodon, etc.) which have been supposed by M. Gaudry and 
other anatomists to belong to the Didelphia, or retain traces of their 
Didelph origin, agree in not having certain peculiarities which are 
essentially characteristic of a Marsupial skull. In none is the jugal 
so large as to reach the lachrymal in front, and pass beneath 
1 «Nouvelles Archives du Museum d’ Histoire Naturelle de Paris,” vol. vi. 1870, 
eo le7, 
‘i 4 Hy cit. p. 32. The brain of Oxyena, as well as of Stypolophus, was similar to 
that of Arctocyon and Proviverra (Cope, op. eit. pp. 72 and 107). 
3 “The Anatomy of Vertebrated Animals,” p. 447. 
4 Gervais—‘‘ Nouvelles Archives,’’ 1870, p. 127. 
