1910.] RelotionK of the CirodoHts to Carnivorous Marsupials. 299 



"It would appear from the present trend of evidence that we shall be 

 compelled eventually to return to the old idea of a direct Marsupial ancestry 

 of all the Monodelphian orders" (p. 335). This does not mean that "the 

 living Marsupials are those ancestors" since they have a number of "modern- 

 ized features" among which are cited the mode of replacement of the teeth, 

 the increased number of incisors in Polyprotodonts, and the inflected 

 mandibular angle. 



Dr. Wortman holds that the "Mesozoic representatives of the carnivo- 

 rous Marsupials are not far removed from the hypothetical forms, to which it 

 seems to me, the present evidence points with no doubtful signs, as the 

 ancestors of the Carnivora " (/. c, p. 335). By "Mesozoic representatives 

 of the carnivorous Marsupials" he seems to refer to Cretaceous Didelphoid 

 forms, since he states (pp. 33G-337) that "just what the Cretaceous JNIarsu- 

 pials, when more fully known, will show wath respect to these characters 

 [namely, the relations of the milk and permanent dentitions, the inflected 

 angle of the jaw, etc.] cannot now be predicted; but we do know that such 

 a type as Didelphops Marsh, in its dentition and palate, resembles the living 

 carnivorous Marsupials, and it is to some such type in particular that I would 

 refer the origin of the Creodonta." In another passage (1901, p. 282) he 

 states: "Present evidence points to the fact that the two groups [Creodonta 

 and Carnassidentia] probably arose side by side from the Mesozoic Marsupials 



" And again (1902, p. 143) he says: "That they [the Creodonta] were 



derivatives or offshoots of any preexisting groups of Placentals or Eutherians 

 is exceedingly unlikely. ..." "On the contrary, all the facts point very 

 strongly to their origin, along with Carnassidentia, from Implacental or 

 Marsupial Metatherians. It is likewise conceivable that from this same 

 general substratum the other Eutherian orders arose" (p. 144). 



In brief, Dr. Wortman seems to hold that the Creodonta, Carnassidentia 

 [Carnivora Fissipedia + Palseonictidte + Viverravidse], Insectivora and 

 perhaps other orders have been derived independently from carnivorous 

 implacental Metatheria of the Mesozoic era, typified in palate and dentition 

 by the Cretaceous Didelphops. The opposite conclusion, which is defended 

 in the present chapter, embodies the following propositions: 



(1) That Lower Eocene Creodonts, and Carnassidents were closely 

 related to each other by virtue of derivation from Mesozoic Insectivorous 

 Placentals. 



(2) That the immediately ancestral family of these primitive placentals 

 was not fully carnivorous but insectivorous-carnivorous; not implacental 

 but more probably with both allantoic and yolk-sack placentae; not Creta- 

 ceous ]\Iarsupials with four molars and three premolars on each side and 

 wdth large palatal vacuities, but possibly Cretaceous Insectivores, allied on 



