310 Bulletin America)) Museum of Natural History. {YoX. XXVII, 



But the transference of the MiacitUie to the Fissipedia is demurred to by 

 Matthew upon three grounds. First because the Miacidse, as stated above 

 were inckided by implication in the original definition of the Creodonts; 

 secondly, because they are separated from their descendants among the 

 Fissipedia and allied to the Creodonta by the possession of many primitive 

 characters {e. g., the scaphoid, lunar and centrale, although closely appressed, 

 have not yet fused into a single bone) ; thirdly, because of the existence of 

 certain forms recently described by Matthew which tend to ally the Miacidte 

 with the Arctocyonidpe. 



Apart from this new evidence, there seems to be other reasons also (Alat- 

 thew, 19U1, }). 7) for placing the Arctocyonidje in the Creodonta Adaptiva 

 (Eucreodi) in coriipany with the Miacidfe: («) The manus of Clccnodon, a 

 Basal Eocene Arctocyonid (Matthew, 1901, fig. 6, \>. 7) foreshadows the 

 Fissipede type in the fusion of the centrale with the scaphoid and the close 

 appression of the scaphoid and lunar, the three bones, conjointly having the 

 appearance of a scapho-lunar-centrale, rather resembling those of the 

 Miacid Oodectes, as figured by Wortman (1901, p. 154); and contrasting 

 with the same bones in the other Creodonts. (/>) The divergent hallux and 

 pollex is a primitive character retained partly in the Fissipede Ccrcoleptes 

 (Matthew), (c) The claws also are narrow and compressed, as in jNIiaciiUie, 

 and contrast with the fissured claws of the Mesonychidae, Oxysenida?, and 

 Hyaenodontidae (Matthew). 



The Basal Eocene Arctocyo7i certainly differs from the typical Miacidae 

 in its extremely small brain case, a feature which also distinguishes the 

 Fissipedia from the earlier Creodonta. But this hardly disproves a close 

 alliance between the Arctocyonidae and Miacidae. I'here is cvmiulative 

 evidence that the progressive improvement in the brain of Tertiary phyla, 

 if it could be followed backward into the Basal Eocene and Cretaceous, 

 would lead in every instance into a very lowly type of brain, encased in a nar- 

 row brain case. The evidence given in the preceding chapter tends to show 

 that certain lowly brained Mesozoic Insectivora gave rise to the large brained 

 Menotyphla (p. 272) and to many other Placental orders. The brain case 

 of Arctocyon is of course very small, but it is hartlly if at all smaller in the 

 Lower Eocene Miacid Viverrav)is protenus (cf. Matthew, 1901, j). 9, fig. 1). 



It seems in short to be largely a matter of definitions whether the Miacidae 

 shall be included in the Creodonta or in the Fissipedia. 



Additional evidence of close relationship hetiveen tJie tivo suborders. 



Additional evidence that the Creodonta and Fissipedia are closely related 

 is furnished by the agreement in the general arrangement of the cranial 



