ABSTRACTS OF PAPERS 215 



through the efforts of Prof. O. C. Marsh. For this carnivore I proposed the 

 name Pliocyon marshi. Subsequently, in the same Journal, for January, 1922, 

 I substituted the name Arwocyon. 



The presence of this lower jaw in Middle Pliocene deposits of the New 

 World is exceedingly interesting, as it is the only specimen of its kind de- 

 scribed or reported from the ancient fauna of North America. 



Structurally, Arwocyon is remarkably close to Simocyon primigenius Roth 

 and Wagner from the Pikermi deposits (Upper Miocene) of Greece. The 

 faunal affinities of the Pikermi genera are with those of Africa rather than 

 with Europe, but we also find a similar faunal phase eastward in Samos and 

 at Maragha, Persia, while in general the fauna of the latter approaches very 

 closely to that of the Pliocene of the Siwaliks in southern Asia and of China. 



In the Pliocene, Asia and North America were connected by land and inter- 

 continental faunal migrations took place. Owing to the general eastward 

 trend of the fauna, as mentioned above, it is not unreasonable to suppose that 

 the carnivores also followed the other groups, and that there might have been 

 a concentration of carnivore types in the constricted region of this "game 

 trail" at what is now known as Bering Strait. During the gradually increas- 

 ing cooling of the northern region in the Pliocene, it became necessary for the 

 fauna in the main to migrate southward — a movement which, if this theory 

 be true, was carried on by Arwocyon as far south as Oregon. Therefore my 

 view at present, and Professor Lull is in agreement with it, is that some of 

 the members of the genus Simocyon migrated from southern Europe through 

 Asia and into North America during the latter part of the Upper Miocene and 

 the first half of the Pliocene, and that the time involved was sufficiently long 

 for the former representatives of Simocyon to develop into Arwocyon. 



On the other hand, if Arwocyon is an autochthonous form, then we must 

 place it in the pseudo-canoid phylum, namely, those with the trenchant-heeled 

 inferior molars, wherein we find Daphcenus, Temnocyon, Enhydrocyon, Cyon, 

 Icticyon, and Lycaon. 



If this lower jaw on which Arwocyon is established had been collected in 

 the Pliocene of Europe, I should have no hesitation in referring it to the genus 

 Simocyon or possibly to a subgenus under it, and if Arwocyon should finally 

 prove to be autochthonous, then it will be one of the most remarkable cases of 

 convergence on record. 



A summary of the results of the American Museum Expedition last 

 summer in the Snake Creek fossil quarries, Miocene and Pliocene of 

 western Nebraska, was given under the following title: 



SNAKE CREEK FAUNA 

 BY W. D. MATTHEW 



There was then presented by title 



PHYLLOGEVY AND NOMENCLATURE OF THE PROBOXCrDEA 

 BY HENRY FAIRFIELD OSBORN 



The session was then adjourned. 



