330 MR. W. H. FLOWER ON THE ANATOMY [Dec. 9, 
few, but deeply cut, and characteristic sulci*. 1. The fissure of Sylvius 
(e) slopes upwards and backwards to about two-thirds of the distance 
between its commencement and the margin of the great longitudinal 
fissure, and then ends abruptly without joining the antero-temporal. 
2. On the frontal lobe is a deeply marked fissure (the supero-frontal, 
6) running transversely backwards and outwards, bent at an obtuse 
angle in the middle. 3. Separated by a wide interval (antero-parietal 
gyrus) from this is the simple, straight postero-parietal (fissure of 
Rolando, d). 4. Behind this is the suleus bounding the upper border 
of the angular gyrus, having the form of a broad pointed arch. 5. 
The long and deeply marked antero-temporal sulcus (f) runs from 
the apex of the temporal lobe, upwards beyond the end of the fissure 
of Sylvius, curving slightly forwards at its termination near the point 
of the aforesaid arch. 6. Of the temporo-occipital (external perpen- 
dicular, /) the traces are but small ; its commencement is seen above, 
in a notch on the border of the hemisphere, and again there is an in- 
dication of it at the posterior termination of the angular sulcus, but 
it does not interrupt the perfect superficial continuity from the pa- 
rietal to the occipital lobe of both first and second external annectent 
gyri (13 and 14). In this respect Pithecia agrees with Ateles rather 
than Cebus. The absence of this fissure (so constant in the Old World 
Apes) in all the smaller American Monkeys, and its imperfect condi- 
tion in others of the family, show that it is a less important character- 
istic of the Simian brain than is the antero-temporal or even the an- 
gular. 
On the inner face of the hemisphere (fig. 4), the sulci present the 
Fig. 4. 
ordinary and typical character ot the Primatial type of brain, in a 
simple form. The calloso-marginal sulcus (7) is very well marked, 
and inclines upwards almost to the margin of the hemisphere at its 
hinder end. It has several small secondary sulci connected with it. 
The oceipito-parietal (internal perpendicular, *) runs down from the 
margin of the hemisphere, and then bends abruptly forwards. That 
most characteristic sulcus, the calearine (/), the bottom of which 
corresponds with the hippocampus minor in the posterior cornu of 
the lateral ventricle, is deeply cut, runs directly backwards, and 
* For the nomenclature of these parts of the brain, see a paper by Prof. Huxley, 
“On the Brain of Aleles paniscus,” Proc. Zool. Soc., June 11, 1861. 
