348 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



rected forward the two principal fissures of the mesial surface. This lobule ap- 

 pears to be constant in position and relations, not only throughout the Carnivora 

 but also in the Ungulata, and I propose for it the name of tentorial lobule. It is 

 included between the posterior extremities of the fissura splenialis, s p, and the pos- 

 terior rhinal fissure, p r h. 



The mesial arched fissure, m a, is well marked. Its superior branch, the fissura 

 callosalis, at first sight appears to be separated from the inferior or hippocampal, by 

 the backward extension of the splenium corporis callosi. A distinct fissure can, 

 however, be distinguished connecting them together. There will be perceived the 

 mesial parieto-frontal surface, besides the fissura splenialis, one or two other fissures, 

 Plate XLV, fig. 8, which are simply vegetative repetitions of the splenialis, which 

 evidently corresponds with the mesial occipito-frontal of the Primates. Of these 

 the upper is called the fissura marginalis, m r. They should be regarded, I believe, 

 as vegetative repetitions of the fissura splenialis. We have in the same figure of 

 the brain of the lion a vegetative repetition of the fissura postrhinalis, p r h. 



CONVOLUTIONS OF THE UNGULATE BRAIN. 



The convolutions of the Ungulata, whilst quite complicated in detail, are con- 

 structed upon a relatively simple general plan. A fissure of Sylvius, or at least a 

 vertical fissure that takes its place in position, is present in some, Plate XLVII, 

 fig. 2, whilst in other cases no signs of its presence, at least in the adult, can be de- 

 tected, Plate XLVI, figs. 2 and 6, Plate XLVII, fig. 8. The fissures pursue on the 

 lateral surface a longitudinal or more or less arching position, and may be compared 

 with the corresponding fissures as found in the brain of the Carnivora. These con- 

 volutions of the lateral surface appear to be thrown into more or less similar sec- 

 ondary folds on each side of the position of the Sylvian fissure, very much as the 

 folds of a coat sleeve assume a more or less symmetrical or balanced character on 

 each side of the elbow joint when the arm is bent. This is well seen in the brain 

 of the giraffe, Plate XLVI, fig. 11. On each side of the Sylvian fissure are seen two 

 small arched gyri, a, and beyond these on each side, two more less pointed ones may 

 be seen, b. From the extremities of these, two lobules, c, proceed, one of which 

 reaches the posterior extremity of the hemisphere, the other the anterior, where 

 they become continuous with the two ends of a convolution which arches over the 

 whole course of the lower. The same general tendency may be traced in the brains 

 figured on Plate XLVI, figs. 2, 6, and 8 and Plate XLVII, 'figs. 2 and 8. 



The plan of the mesial surface is identical with that found in the Carnivora. 

 There is no posterior horn to the lateral ventricle, and therefore no occipital lobe ; 

 but the wedge-shaped lobule, lobulus tentorii, or tentorial lobule as we have termed 

 it, is constantly present, having the same general appearance and preserving the 

 same relations to the fissures found in this region as in the, carnivorous brain. It 

 may be seen as found in the peccary, Dicotyles labiatus, Plate XLVI, figs. 1 and 3, 

 in the caribou, Plate XLVII, fig. 3. By comparing fig. 3, Plate XLVI with fig. 8, 



