122 



ANATOMY OF VERTEBRATES. 



/ and g bend outward anteriorly, in Rhinoceros, in a more definite 

 way than in Equus. The anterior lobe, marked off by the short 

 fissure, 14, is relatively larger in every dimension in the great 

 Perissodactylcs, and is broader and deeper in the Horse than in 

 the Rhinoceros. The tract of the inner or mesial surface of the 

 hemispheres above the callosal fissure, fig. 100, 7, is impressed by 

 the parallel * marginal ' fissure, ib. 6, in both large Perissodactyles ; 

 and the callosal fold so defined is subdivided by a secondary 

 intermediate ( supercallosal ' fissure, ?', more continuous in the 

 Rhinoceros than in the Horse, into the ( callosal proper,' k, and 

 the supercallosal, k', folds. Beside the falcial fissure, 15, there is 

 a prefrontal secondary fissure ; and the septal or postfalcial sur- 

 face, p', q*, is extended by secondary fissures. The increase and 

 complexity of the upper convoluted surface of the hemispheres in 

 the larger Perissodactyles are due to the full establishment of 

 primary fissures, upon the plan sketched out in Hyrax, to their 

 more wavy course, and to the superaddition of secondary fissures, 

 indicated by interrupted lines in figs. 97 and 98. 



In passing from the Pigmy Musks to the brains of larger Artio- 

 dactylcs, we find the fissure which is feebly indicated at 10,, fig. 



101 102 103 



Ccrvus. 



Giraffe. 



Tragulus. 



101, Tragulus, fully developed in figs. 102 and 103, and di- 

 viding the triangular tract into the oblique folds / and g : which I 

 hold to include the same parts of the cerebrum as the more longi- 

 tudinally disposed folds lettered g, I, m, in Carnivora. In some 

 small Cervidce the secondary fissure, 11, is not present : in most it is, 

 as also in the hollow-horned Ruminants, Giraffe, Camel-tribe, fig. 

 105, Auchenia, Suid<z,fig. 104, and Hippopotamus. The lambdoidal 

 fissure, 13, retains its character, as in Tragulus, viz. short, ante- 

 riorly convergent, and continued on the inner surface of the hemi- 



