NERVOUS SYSTEM.- VERTEB&ATA. 153 



Carnivore, Ungulate, and Primate brain respectively, in 

 which no exact correspondence exists. We know from the 

 distribution o the claustrum that the exact cortical areas 

 from which the lips of the Sylvian fissure are formed in 

 different higher Orders [or even Suborders and Families 

 compare the Cynoid, Arctoid, and Pinniped Carnivores and 

 the progressive modifications in their various families] are 

 not strictly homologous in different mammals ; so that if 

 we use the term u Sylvian " for all these various types of 

 fissure, we are also justified in using it for the fissure o the 

 Spiny Anteater's brain, which is clearly caused by analo- 

 gous factors of growth, without thereby implying any 

 strict homology in the cortical areas which form its lips. 

 It will avoid much confusion, however, if we call this 

 sulcus (fig. 43, SYL.F.) " pseudosylvian." 



Fig. 43. (Nat. size.) 



The sulci of the neopallium of the Spiny Anteater vary 

 very considerably in different individuals, and there is no 

 clue to indicate whether any of them should be regarded 

 as the representative of a sulcus of other mammalian brains. 

 On the other hand, the arrangement of the sulci suggests 

 that they might be due to purely mechanical factors 

 operating in an uniformly growing pallium, the longi- 

 tudinal expansion of which is restricted. 



The most constant of all the sulci are three distinguished 

 as a, /3, and ifr in the diagrams (figs. 38 and 43). 



[The figures (38, 39, and 43) illustrating this account are 

 drawn from the preceding specimen (D. 191) in order that 

 both hemispheres might be represented. The description, 

 however, applies more especially to this specimen (D. 192), 



