1910.] "Meseutheria" and "Cceneutheria." 459 



comparative anatomy and embryology is at fault all foi-ins with large well 

 furrowed cerebra and relatively small rhincnce])hal()ii must have been 

 derived from forms with smooth small cerebra, large rhiueneephalon and 

 large fully exposed cerebellum — a type of brain ])reserved in the more 

 primitive Insectivores, in the Meseutheria and in the earliest forerunners 

 of the Carnassident Carnivores (Didymirtis protcnns; cf. ]). 310). 



Upon such differences in brain structure Bonaparte divided the Mam- 

 malia into the Ineducabilia and Educabilia, and Owen placed mankind in a 

 separate grand division, the " Archencephala." 



If these quantitative differences in brain type imply divergence in origin 

 rather than differences in degree of development, they ought to be ac- 

 companied by widely divergent non-adaptive characters in various parts 

 of the organism. 



(2) The ancestors of the Fissipedia (Carnassidentia) had all the ordinal 

 characters of the Creodonta. The Eocene Miacidee (Viverravidje) as 

 described by Matthew (1909) are prototypal (p. 309) to the Fissipedia in the 

 dentition and in the characters of the skull, cranial foramina, manus and 

 pes, etc. If the Miacidtie are to be regarded as Creodonts then at least 

 one Meseutherian group is shown to be prototypal to a Cfieneutherian group. 

 If on the contrary the Miacidse are regarded as Cseneutherians, then it is 

 shown that among the earliest Cfeneutherians were forms (Didipnicti.s 

 frotenus) which had a brain case no bigger than that of Arctocijon, a ty})ical 

 Meseutherian. Further, Matthew (1909, pp. 399^00) has shown: first, 

 that certain Miacidae {Pcdaearcionyx) closely resembled the Arctocyonidte 

 in all the parts known, namely the dentition, humerus and terminal phal- 

 anges; secondly, that both in the manus and pes the Arctocyonid genus 

 Clcenodon, foreshadowed the Miacid-Fissiped group in many significant 

 details (p. 310). 



(3) Unless convergent evolution is again deceiving us, the ancestors 

 of the Caeneutherian order Perissodactyla seem to have been related to the 

 ancestors of the Meseutherian Condylarth genus Euprotogonia, because the 

 latter is approximately prototypal to the Perissodactyls in the dentition, 

 carpus and tarsus and all other ])arts of the skeleton (p. 396). 



(4) The ancestors of the Cseneutherian orders Hyracoidea, Embritho- 

 poda, Pyrotheria, Proboscidea, and Notoungulata W'cre probably small- 

 brained Meseutherian protungulates (pp. 369, 382, 410, 411), which were 

 probably rather nearly related in various ways to each other. 



(5) The ancestors of the Ca?neutherian order Artiodactyla (p. 4U4; 

 may be related to the ancestors of the Meseutherian Creodonta-Mesonychida% 

 because the latter are ap])roximately prototypal to the former in many 

 details of the skull, dentition, limbs and feet, carpus and tarsus. 



