374 KK. G. ELLIOT SMITH ON 



In a mesial sagittal section (fig. 34) we can correlate the organ with that oi Xenitru n 

 The dee.]) Jissura 2}riwa cuts into the anterior surface and sejoarates the anterior lobe from 

 the central lobe. Upon the anterior surface (fig. 35) we find the anterior lobe bounded 

 by the semicivculeiv Jissura prima and subdivided by a few subsidiary sulci. 



riff. 36. 



.fiea. eecuDda 



lob. poBt. 



medulla obloDg. 



Caudal Burfaeo of brain of Chlamtjdophoi-as to show the cerebeUum. Eiilargetl 2 diam. 



Toward the lower part of the posterior surface we find the /issttra sectmda separating 

 the small posterior lobe from the central lobe. In a view of the posterior surface (fig. 36) 

 we see this fissnra secunda as a small semicircle. A few shallow fvirrows begin at the 

 lateral margin and extend for a short distance toward the mesial plane. 



The meaning of all tliese data will be In-iefly discussed in the conchiding part. 



General Considerations. 



In reviewing all the data Avhich I have been able to collect and examine in the fore- 

 going pages, the many imperfections of the record are only too patent. Our knowledge 

 of the adult brain, even so far as its macroscopic features are concerned, is far from 

 jDcrfect, and we have only the merest scraps of information concerning its developmental 

 history in the different genera. Yet this knowledge, in spite of its fragmentary nature, 

 is not altogether lacking in importance. For if it does not j)ermit us to positively localize 

 the members of this group in the mammalian series, the evidence of cerebral anatomy 

 enables lis to definitely refute many beliefs concerning the position of the Edentata which 

 even the wealth of palseontological discovery Avithin recent A^ears has been unable to 

 shatter. In addition to this negative A^alue, the testimony of the brain indicates with 

 some degree of proliability the direction in which we must look for the nearest allies of 

 the heterogeneous group Avhich we are discussing. 



"While recognizing that the evidence of cerebral anatomy often possesses a decisive 

 taxonomic value, we cannot be blind to the fact that in many cases, without the sujiport 

 of the testimony of other anatomical systems, we could only vaguely hint at the position 

 of a mammal from the character of its nervous system. Tluis, while we attach considerable 

 importance to the exact configuration of the brain in Myrmecophaga, we could not 

 suggest any kinshijj of tlie Armadillos with this Ant-eater uj)on the evidence of its 

 cerebi'al anatomy, if we were not aware of the peculiar Xenarthrous nature of its vertebriB. 

 At the same time it is quite possible that, if we were acquainted with the pallial configu- 

 ration of Friodon, w^e might be able to say decisively that the Giant Armadillo is a 

 relative of the Great Ant-eater upon the evidence of the brain alone. T'he merest tyro 

 could recognize at a glance the brain of a member of either of the great Ungulate or 



