THE BEAIN IN THE EDENTATA. 387 



According to this writer, tliese peculiar mammals, which lie calls Ganodoida *, show a 

 series of modifications which indicate tlie change from a typical mammal to a highly 

 specialized form which is practically identical with the Edentate type. He concludes 

 that the South- American Edentates of the present day sj)rang from this Ganodont stoci^, 

 which began with Hemigamis and lead up to Styliuodon, and at the beginning of the 

 Santa Cruz epoch they wandered from the Northern to the Southern continent. The 

 distinctions between the members of this Ganodont stock and the Creodonta and Tillo- 

 dontia are so slight, that we find different members of Wortman's group variously 

 included in the Creodonta and Tillodontia by Cope, Marsh, and von Zittel, among other 

 palaeontologists. 



It is not for me to express an opinion either for or against the evidence of a Ganodont 

 origin for the Edentata ; but this brief review of the recent tendencies of American 

 palaeontology makes it clear that in suggesting, upon the evidence of the data collected 

 in this memoir, an origin of the Ant-caters from some post-Creodont stock which has 

 since then diverged from the Unguiculate stem, we are not contradicting palseonto- 

 logical evidence, but that, on the contrary, we are to a very considerable extent supported 

 in our contention by this. 



This leads lis to the consideration of the position of Ori/cteropus. If the brain of 

 Orycteropus were given to an anatomist acquainted with all the other variations of 

 the mammalian type of brain, there is probably only one feature which would lead 

 him to hesitate in describing it as an exceedingly simple Ungulate brain. That one 

 feature is the high degree of macrosmatism. But we know how readily the degree 

 of macrosmatism vai'ies with the change of habit of the animal. Within the family of 

 Ant-eaters we have seen the terrestrial Myrmecopliaga exhibiting a high degree of 

 macrosmatism, and the arboreal Cyeloturus showing an equally noteworthy reduction in 

 the size of its rhinencephalon. We may therefore associate the high degree of macros- 

 matism of Orycteropus with its peculiar mode of life, and regard it as a functional 

 modification of little taxonomic value. Such being the case, the similarity of the brain 

 to that of the macrosmatic IIoscJius is of exceptional interest, when we remember that 

 the latter mammal retains " characters belonging to the older and more generalized 

 types of ruminants " f and is a relative of the primitive hornless deer of the lower 

 Miocene +. The characters of the brain of the Aard-vai'k which lead us to associate it 

 with the Ungulate type are the horizontal direction of the whole rhinal fissure {i. e. the 

 absence of a downgrowth of the pallium) and the horizontal arrangement of the repre- 

 sentative of the suprasylvian sulcus. The features of the region where we find the 

 fossa Sylvii in Myrmecophaga, and its similarity to the peculiar arrangement of the 

 Sylvian fossa in Mosclms moschjfems §, add further testiiuony to this Ungulate likeness. 



At the same time we must admit that it is far inferior to existing Ungulates in regard 



* J. L. Wortman, " Psittacotherium, a Member of a New and Primitive Suborder of the Edentata,'' Bull. Amer. 

 Mus. Nat. Hist. vol. viii. art. xvi. 1896. 



t Flower and L)-dekker, 'Mammals, Living and Extinct,' 1891, p. 314. 

 t A. S. Woodward, ' Tertebrato Palaeontology,' Cambridge, 1898, p. 365. 

 § W. H. Flower, Proc. Zool. Soc. London, 1875, p. 175. 



