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, 

 h) 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 sulcus 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 (/) 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, h) 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 Pifhecia 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. 



i^^<r\\i 



[ .n^~ 



.j^ 



ordinary and typical character ot the Primatial type of brain, in a 

 simple form. The ealloso-marginal sulcus (^} 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 occipito-parietal (internal perpendicular, k) runs down from the 

 margin of the hemisphere, and then bends abruptly forwards. That 

 most characteristic sulcus, the calcarine (I), 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 Ateles paniscus," Proc. Zool. Soc, June 11, 1861. 



