118 



ANATOMY OF VERTEBRATES. 



one, as if to subdivide the medial tract, fig. 83, /, and is continued 

 far forward in the larger FcUdce, though shallow like a secondary 

 fissure. The sylvian fold, e, e', also begins to be subdivided by the 

 secondary fissures s', s', fig. 91, which are more fully established, 

 arching over the sylvian fissure, at s', in the Canidce, fig. 92, Fox. 

 On the inner surface of the hemisphere the supercallosal fissure, 

 fig. 86, ?', in the Cat, rises anteriorly diverging from the callosal 

 one, 7 ; the frontal fissure, n, extends backward into their inter- 

 space : the marginal fissure, ib. 6, runs parallel with the super- 

 callosal one, 7* ', and is longer in the larger felines ; in which most 

 of the primary folds are impressed by short secondary fissures. 1 



The cerebrum of the Canidce, figs. 89, 92, Fox, is longer and 

 narrower anteriorly than in Felidce, fig. 83. The frontal fissure, 

 fig. 89, 14, marks out a longer anterior lobe : the medial fold, ib. 

 Z, /, is more longitudinal, less bent outward anteriorly ; the lateral 

 or supersylvian fold g, y, has a like character : the sylvian fold, 

 fig. 92, e, e' ', is subdivided by the secondary fissure, s', arching 

 over the sylvian one, 5. The coronal fissure, 12, is now recognis- 

 able. The anterior lobe is equally divided by the frontal fissure, 

 fig. 89, 14, into the postfrontal tract, ?i, and the prefrontal, ri' } n*. 

 Most of the primary folds are marked by secondary fissures, and 

 the number, extent, and depth of these chiefly distinguish the 

 brain of the Dog from that of the Fox. 



The brain of the Bear ( Ursus) is more oblong than that of the 



Fox. The frontal fissure marks out as long 

 an anterior part, in which the subfrontal n' 9 

 midfrontal n" ', and superfrontal n'" ', tracts are 

 indicated by secondary fissures : but the me- 

 dial fold, /, is more extensively bent outward. 

 The medilateral fold, m, is still more bent out- 

 ward anteriorly from the longitudinal course. 

 Secondary fissures impress the surface of 

 several of the primary folds, especially the 

 broad anterior part of the medial one. The 

 cerebrum attains its greatest relative size 

 and complexity of structure, in the present 

 group, in the Seal family, fig. 93. The 

 horizontal contour of the brain is almost 

 circular, and the surface of the hemispheres 

 offers, at first view, numerous convolutions ; 

 but a comparison of their relative depth serves to distinguish the 

 secondary from the primary ones, which latter are the follow- 



1 XLVII-. pi. 20, figs. 1-3 (F. jiibata). 



93 



Seal (PJwc(i). Upper surface 

 of right hemisphere. 



