ON THE BRAIN OF ATELES PANISCUS 495 
and the more transverse direction of the fissure of Rolando, are very 
remarkable ; for the skulls of the two specimens show no particular 
difference of form. In the unaltered brain, figs. 1, 3, 4, the narrowness 
of the frontal lobes anteriorly, the excavation of their orbital faces, 
and the flatness of the superior contour are especially worthy of 
notice. Viewed from above, no part whatsoever of the cerebellum is 
visible, either at the sides or behind ; while a profile view shows that. 
the cerebral hemispheres projected, for at least j;th of an inch, behind 
the posterior edge of the cerebellum. Whether this represents the 
total amount of cerebral overlap or not, I cannot say, in the absence 
of a vertical section of an AZe/es’ skull; but it is amply sufficient to 
prove that, even accepting as the definition of the posterior lobe the 
novel formula “All that part of the hemisphere which covers the 
posterior third of the cerebellum and passes behind it,” <Adeles is 
provided with a well-developed posterior lobe. 
In this respect, as I have already said, it resembles all the Old 
and New World Szmze which have yet been examined,—the only 
genus, within my knowledge, which even comes near to presenting an 
exception being A/ycetes. I have not, indeed, had the opportunity of 
dissecting the brain of this monkey (nor has M. Gratiolet been 
enabled to give any account of it); but the Curator of the Hunterian 
Museum having kindly permitted me to have a vertical longitudinal 
section of the skull of a AZycetes made, I found not only that the 
plane of the tentorium (and consequently the inferior margin of the 
posterior lobes of the cerebrum) had a much greater inclination than 
in any other Simian (making an angle of as much as 45° with the 
base of the skull), but that the cerebral overlap, measured in the 
manner described by me in the Adkeneum for April 13th, 1861, does 
not exceed ,;th of an inch, though the maximum length of the 
cranial cavity is 2'4 inches. Notwithstanding this reduction of the 
posterior lobe, however, the contrast between A/ycetes, as a true 
Simian, and a Lemur is very striking, especially if both be simul- 
taneously compared with some lower Mammal, such as the Dog. The 
occipital foramen in J/ycetes is situated altogether upon the posterior 
face of the skull, and the condyles look completely backwards, as in 
the Dog; while the occipital crest is placed as near the postero- 
superior margin of the skull as in that animal. In both, the posterior 
face of the skull looks backwards, and not appreciably downwards. 
But in the Monkey the inclination of the tentorium, large as it 
is, is far less than in the Dog. The inner face of the occipital bone 
beneath the tentorium is not excavated, and the cerebral lobes 
projected beyond the cerebellum when the palate was horizontal. In 
