124 



ANATOMY OF VERTEBRATES. 



The sylvian, e, and supersylvian, g, folds are more undulated, 

 or interrupted, and less neatly defined in the Ungulata, at least in 

 the larger species, than in the Carnivora. They are still less de- 

 fined in the richly convoluted brains of the Proboscidia, fig. 108, 

 and Cetacea, fig. 94. 



With regard to the Ungulata the choice of 10 or 13 for the medi- 

 lateral fissure 10, fig. 91, in Unguiculata, may long be undecided, 

 and consequently the choice of 10 or n, for the homologue of the 

 lateral fissure 1 1 ; but the determination of the supersylvian fissure, 

 8, will probably be accepted, and on this basis, with the relations of 

 13, i3 r , figs. 96 — 107, to the inner surface of the hemisphere, I 

 am now, as in 1842, guided in the above determinations. 



In the Lemuridce the cerebrum does not extend over the whole 

 of the cerebellum, fig. 109, Aye-aye : it does so in both platy- 

 rhine and catarhine groups : but there are species of Quadrumana 

 more diminutive than any of the Ungulate Mammals, and with this 

 infantile character is associated a foetal smoothness of the cerebral 



Midas. 



Foetus, 5 months. 



Aye-aye. 



surface, irrespective of the relative size of the hemispheres, figs. 

 109 and 116, Midas, 



Every quadrumanous brain shows the ectorhinal, fig. Ill, 2, 

 entorhinal, ib. 3, hippocampal, fig. 110, 4, callosal, 7, marginal, 6, 

 and sylvian, fig. 109, 5, fissures. In the Galagos and Slow Lemurs 

 a beginning of other fissures appears on the upper surface ; but 

 they are not fully marked until the species attain the size of the 

 Aye-aye and Lemur. 



In Chiromys the fissure, fig. 109, n (Aye-aye), 1 commencing in 

 advance of the posterior border of the hemisphere, advances, slightly 



1 or. pi. xii. figs. 3, 2; 

 Carnivora. 



it combines, also, the character of the mcdilateral, 10, in 



