THE BKAIN IN THE EDENTATA. 335 



upon the two liemispheres. From the postero-ventral corner of the hemisphere a 

 shallow furrow ascends upon the left hemisphere for three or four millimetres, and upon 

 the Yis;ht hemisphere a more definite sulcus in the corresponding place. We may call 

 this the sulcus e. 



Upon the right hemispliere of our type-specimen there is a faint trace of a vertical 

 furrow midway between the sulcus S and the fossa Sylvil. We may refer to this as the 

 sulcus n. Thei'e is no sign of it upon the left hemisphere. 



In the figure of the lateral aspect of the brain which Gervais gives there are two 

 extensive vertical sulci upon the postero-ventral area of ])allium, and a trace of a third. 

 The exact homologies of these sulci are somewhat doubtful. It is possible that the most 

 caudal represents an exceptionally well-developed sulcus e, and the more anterior the 

 sulcus 5. 



Upon the left hemisphere of our type, as Avell as in the specimens figured by Gervais 

 and For]:)es, there is a shallow horizontal furrow midway between the anterior part of 

 the sulcus -y and the narrow tapering extremity of the fossa Sylcil. This may be 

 distinguished as S'. 



If we compare the arrangement of sulci upon the cranial surface of the hemisphere of 

 Myrmecophaga with the principal and more constant fissures which are found upon the 

 pallium in the Carnivora, we must admit that the resemblance is so close that it suggests 

 somethins' more than a mere coincidence. The similarity is so striking? that we do not 

 hesitate to compare one by one the sulci of Myrmecophaga, Avith sulci which are 

 obviously homologous in almost any Carnivore. The resemblance is perhaps more 

 striking in the case of the small Carnivores, because soaallness implies a simplicity in the 

 arrangement of the sulci. In the lai'ger Carnivores the pattern becomes complicated by 

 the introduction of numerous subsidiary and morphologically unimportant sulci. But 

 in such a brain as that of Proteles, of which Flower has provided its with admirable 

 illustrations*, we find hemispheres devoid of all the subsidiary sulci and only the 

 important sulci remaining. In such a type we find the homologues of the sulci of 

 Myrmecophaga preserved, while most of those not represented in the brain of the 

 Ant-eater are also lacking in the small Carnivore. For purposes of comparison, however, 

 I shall refer to the better-known l)rain of the Dog, of which many admirable descriptions 

 are aAailablc. 



In the Dog we find a fissure arising from the point of junction of the anterior and 

 posterior rhinal fissures, and extending obliquely upward and backward. It is customary 

 among writers to call this the " Sylvian fissure," but Ave must accept this term, which is 

 borrowed from human anatomy, with some reservation. The so-called Sylvian fissure of 

 of the Dog's brain is rather an early expression of those factors Avhich, in the human 

 bi"ain, produce large folds of pallium that overlap an intermediate area of sunken 

 cortex, and by their meeting form a fissure. 



The so-called Sylvian fissure in the Carnivora ought to be regarded as analogous 

 rather than strictly Jiomologous to the true or human Sylvian fissure. In the Carnivora 



* W. H. Flower, " Anatomy of Proteles," Proc. Zool. Soc. Londcn, 1869. 



46* 



