304 Bullfthi American Mu.^eum of Natural History. [Vol. XXVII, 



account the peculiar displacement of the ectocuneiform beneath the cuboid 

 in the pes of the Thylacinidse, the astragalus of these and of all known Mar- 

 supials is much lower in development (p. 454) than it is in the Basal Eocene 

 Creodonts, and quite unlike that of the very family, the Mesonychidae, which 

 is supposed by Dr. Wortman to lie nearest to the Marsupials. 



Dr. Wortman's view that in the structure of the feet the Arctocyonidae 

 stand "much nearer to the carnivorous Marsupials. . . .than to any Carnas- 

 sident " {op. cit.) evidently refers to general resemblances only, because the 

 carpus and tarsus are radically different in the two groups (c/. p. 310). 

 The tendency to opposibility of both poUex and hallux, which is responsible 

 for much of the resemblance between Cla^nodon and the carnivorous ISIar- 

 supials, is probably merely one of the indications of arboreal ancestry in the 

 central Placentals as well as in Marsupials (pp. 200, 2S8). 



In fine, the case for a direct independent derivation of the Creodonts 

 and higher carnivores from Mesozoic carnivorous Marsupials of the type 

 of Didelphops seems hardly to have been substantiated. 



GENETIC EELATIONS OF THE CREODONTA TO THE INSECTIVORA. 



As shown above Huxley, Cope and many others believed that the Creo- 

 donta were derived from or were closely related to, the Insectivora; but 

 Dr. Wortman has recently challenged this view (1901, p. 335) in the follow- 

 ing words: "There appears to be a sort of vague belief that the Carnivora 

 have arisen from the Insectivora, and one frequently hears the expression 

 ' Insectivore-creodont ancestors.' Now, as a matter of fact, the Insectivora, 

 as we at present know them, are not more primitive than a large majority 

 of the Creodonts; but on the contrary, wdth very few exceptions, all the 

 living Insectivores are considerably specialized, and even those that do exhibit 

 a more or less generalized structure are far removed from the typical ideal 

 ancestor of the Carnivores. Nor do the few known fossil Insectivores help 

 us much towards such a belief, for in all of them, so far as we know, the pecu- 

 liar conformation of the anterior part of the skull is almost as strongly marked 

 as it is in their living representatives. The very general enlargement of the 

 premaxillse and modification of the incisors, with the reduction or disappear- 

 ance of the canine, constitute one of the striking osteological peculiarities 

 bv means of which they may nearly always be distinguished from any known 

 Creodont or Carnassident." 



TJic ancestral Insectivores were more primitive than the ancestral Creodonts. 



That the Insectivora as an order are more priiBitive than any other recent 

 Placental order is a conclusion for which strong evidence has been cited 

 above (pp. 287-292). On the other hand the majority of the living In- 



