Page 456. 
510 ON GELADA RUEPPELLI. 
is frequently absent, and when present is irregular and much smaller 
than in Macacus. 
In the genus Oynocephalus the peculiarities of Cercopithecus are 
observed, except that the caudate lobe is very short, only extending 
half across the right lateral lobe horizontally. The Spigelian lobe is 
also well developed, quite as much or even more so than in Macacus, it 
being thicker than in that genus. 
In Gelada the right and left central lobes are proportioanlly 
larger than in the genera above described. Otherwise it most 
resembles Cercopithecus, differing from it in that the cystic fissure 
is shallow, at the same time that the fundus of the gall-bladder does 
not so nearly approach the inferior border of the right central lobe. 
It resembles Cercopithecus in that the Spigelian lobe is absent, at the 
same time that the caudate lobe is long, in both which respects it 
contrasts strongly with Cynocephalus. The only lobelet is one on 
the right border of the umbilical fissure, which is Macaque-like. It 
differs from Macacus in the obliquity of the inferior border of the 
right central lobe, and in the nearness of the gall-bladder to the 
umbilical fissure, as well as in the absence of a Spigelian lobe and the 
large size of the central lobes. 
The brain of Gelada rueppelli is particularly instructive when 
compared with the beautiful series of figures in Gratiolet’s ‘‘ Mémoire 
sur les Plis Cérébraux de Homme et des Primatés.” Its different 
aspects are represented, natural size, on Plate [31] XXXVIIT. Its most 
marked feature is the relatively small size of the occipital lobe, which 
is about as large as in the Semnopitheci, smaller than in the Oynoce- 
phali, and much smaller than in Macacus as well as Cercopithecus. In 
the two last-named genera this lobe is unconvoluted, or very slightly 
so. In Gelada there is a simple horizontal sulcus (h, h) a short 
distance above its lower border, running from the posterior surface 
some way forward, but not so far as to meet the posterior transverse 
sulcus (¢,c). In Cynocephalus the occipital lobe is more elaborately 
convoluted, 
An inferior horizontal occipital sulcus, parallel to that just de- 
scribed, runs so far forward as to join the major oblique temporo- 
parietal sulcus (4, 0). This is a condition recorded by Gratiolet in 
Semnopithecus mawrus only, the sulcus generally turning upwards to 
end independently. 
The major oblique temporo-parietal sulcus (6, b) commences 
below, near the inferior rounded margin of the temporal lobe, and 
runs upwards as well as backwards to near the middle line of the 
brain. It is joined by the prolongation upwards of the Sylvian fissure 
(a, a), two-thirds from its lower end, it being bent slightly forward at 
the point of junction. 
