PROSENCEPHALON OF MAMMALS. 125 



diverging, to the anterior fourth : and there marks out an incipient 

 coronal fissure, 12: it then bends inward and is continued into a 

 fissure, apparently answering to that marked u in Felis. The super- 

 sylvian fissure, ib. 8, e, n, arches over the sylvian, 5, and postsylvian, 

 9, fissures and folds ; the postsylvian fold, f, being defined by a 

 short postsylvian fissure, 9. Subfrontal and midfrontal folds are 

 indicated by a shallow subfrontal fissure. On the inner surface, 

 fig. 110, besides the hippocampal, 4, callosal, 7, and marginal, 6, 1 

 fissures, a post-hippocampal, 4', bifur- 

 cates, and defines entolambdoidal,^, and 

 septal, s, folds. There is also the begin- 

 ning of a falcial fissure, is', and fold, t. 

 The vertical extension of the natiform 

 protuberance, fig. Ill, f, arrests the 

 ectorhinal fissure, 2, at the sylvian one, 5. lnn 

 The Aye-aye agrees with the Lemurs and Aye-aye. 



all Quadrumana in this respect; the homology of b, fig. Ill, with 

 the basirhinal fold, figs. 52, b' ', 82, h, in Ly- and Liss-encephala, is 

 masked by such interruption of the fissure, 2, in Quadrumana. 



In Lemur proper the lateral fissure (between I and g, fig. 116) 

 is shorter than in Chiromys and is not distinct from the supersyl- 

 vian : in some species it bends outward more abruptly, in so far 

 marking more plainly the coronal fissure, 12, as in higher Quadru- 

 mana, and indicating a longer anterior lobe than in Chiromys : 

 a frontal fissure, 14"', appears there. In the main we recognise in 

 the cerebrum of Chiromys and Lemur, as in that of Carnivora, the 

 primary division of the upper mass of the hemisphere into sub- 

 parallel folds, medial, /, medilateral or supersylvian, g, and 

 sylvian, e ; but, shorter and more bent as they recede from the 

 middle line ; with indications of a longer anterior lobe or tract. 

 The hippocampal fissure is prolonged into a ' post-hippocampal,' 

 fig. 110, \' , as in higher Quadrumana. 



In the diminutive Platyrhine (Midas, GeofFr., figs. 109, 116) the 

 smoothness of the upper surface of the hemisphere is broken only 

 by the extension thereon of the sylvian fissure, 5. In the next 

 stage ( Callithrix) a ( postsylvian fissure,' ib. 9, is added, and 

 the hemisphere may also show a longitudinal fissure, fig. 116, 8, 

 12, curving, like the supersylvian, over the end of the sylvian, 5, 

 and postsylvian, 9, fissures ; but which, in relation to tJ»« inter- 

 hemispheral fissure, corresponds rather with the lateral, fig. 89, 11, 

 of Carnivora : the large anterior tract may show a short frontal 

 fissure, fig. 104, u'". In all the small Platyrhines (Midas, Calli* 

 1 cir. This has also the character of the ' supcrcallosal,' 7', fig. 117. 



