364 PHYSIOLOGICAL SERIES. 



be called the " pseudo-sylvian fissure," to the rhinal fissure. 

 It is therefore the rule in Myrmecophaga (vide specimens 

 D. 282 and D. 283) to find the suprasylvian sulcus 

 converted into a Lemuroid Sylvian fissure. But it may 

 happen (vide specimen D. 281) that the suprasylvian sulcus 

 becomes separated from the " pseudosylvian fissure " and 

 joined to the postsylvian. This anomalous Anteater's brain, 

 therefore, presents exactly the same relationship to the 

 normal Anteater's brain as the brain of the Aye-Aye does 

 to the Lemur's. 



None of the various sulci which Owen, Oudemans, and 

 Chudzinsky have labelled " Sylvian " is the true Primate 

 " Sylvian fissure." The morphological instability of the 

 pseudosylvian furrow (which has also been abundantly 

 demonstrated in the Carnivora, especially in the Viverrida3) 

 is clearly exhibited by these two specimens. In one brain 

 (D. 532) there is a deep, well-defined sulcus extending 

 obliquely upward from the neighbourhood of the rhinal bend, 

 like the pseudo-sylvian fissure of a Carnivore (fig. 208). 

 In the other brain there is no such sulcus, its place being 

 taken by a vertical sulcus (fig. 207, a) and several shallow 

 depressions (j3 and 7). A further variation in the dispo- 

 sition of these regions is shown by Oudeman's specimen. 



There is a simple linear " lateral " (or " intraparietal," 

 as it is called in the Primates) sulcus (fig. 20G). 



The interpretation of the sulci in front of the stipra- 

 sylvian sulcus presents great difficulty. If we attempt to 

 compare them with those of the Lemur's brain, we find 

 a most marked contrast between the two brains, such 

 a- we should hardly expect to find after noting the close 

 similarity of the mesial surfaces of the cerebral hemi- 

 -} 'heres. If, however, we compare the brain of Davbentonia 

 with that of other Mammals (such as the Cat's), then- 

 would l>e little hesitation in labelling the great ti an 

 sulcus (fig. 208, f) in front of the lateral sulcus of one 

 brain (D. 532) " coronal." In the other specimen (D. 5.'U) 

 the representative of this -uleu< is broken up into two 

 fragments, the upper of which () i< joined to <li<- lateral 



