OF WESTERN NORTH AMERICA. 



45 



feet, which we may designate Wind River A, is largely fossiliferous 

 and has yielded most of the important forms found in successive 

 explorations by Wortman^ (1891), Granger (1905), and Loomis^ 

 (1907). Hayden assigned 1,200 feet to an ''upper division," which 

 we may designate Wind River B. This is now believed to contain 

 fossils of a higher type, although the field records are not quite 

 clear and fossils are scarce. 



Preliminary faunal divisions. — (A) Wind River, lower 500 feet, 

 red beds. Lamhdotherium zone. Contains Coryphodon, Phenacodus, 

 EoJiippus, Lamhdotherium, etc. (B) Wind River, upper 800 feet. 

 Bathyojysis zone. Contains CorypJiodon, Phenacodus, also Bathyopsis 

 Palseosyops horealis { = Eotitanops) . 



The B stage approximates the middle Eocene, or Lutetien inferieur 

 of France (Argenton, the older Lissieu and older Egerkingen fissure- 

 formation faunae), and the Bracklesham of England. 



General faunal characters of the Wind River. — Since the faunal 

 levels which undoubtedly distinguish Wind River A and B have not 

 yet been clearly separated, we must consider the fauna chiefly as 

 found on the lower levels, or red beds. First it must be made clear 

 that the Wind River, as compared with either the Wasatch or the 

 Bridger, is a relatively barren formation and has not been so fully 

 explored. 



Archaic or Cretaceous fauna: Of the ancient fauna the Creodonta 

 are represented by 4 families, the members of which are incom- 

 pletely known. Of these the genera {a) Hapalodectes and Pachysena 

 (Mesonychidae), Q)) Tritemnodon (Hysenodontidae), and Oxysena 

 (Oxyaenidae) are somewhat more advanced than Wasatch forms; (c) 

 Limnocyon, a primitive, and Patriofelis, a specialized member of the 

 Oxyaenidae, appear for the first time, animals which are very charac- 

 teristic of the Bridger; {d) Anacodon represents the Arctocyonidae. 



Among the Tillodontia the Wasatch genus Esthonyx persists, and 

 among Taeniodonta (Edentata?) the Bridger genus Stylinodon first 

 appears. The Insectivora are undoubtedly representcvl in Palseic- 

 tops (Leptictidae), Palseosinopa (Pantolestidae), and possibly also by 

 several species of Hyopsodus, all in more advanced evolution stages 

 than those in the Wasatch, but still distinct from the Bridger species. 

 It is noteworthy that Hyopsodus attains its largest size at this time. 

 The reported existence by Cope of Cheiroptera is an error. 



The Condylarthra-Phenacodontidae diminish and disappear. The 

 Amblypoda-Coryphodontidae also diminish and disappear, being 

 replaced by the Amblypoda-Uintatheriidae. Of (^arnivora-Creo- 

 donta, the family Arctocyonidae is represented by Anacodon (vide 



o Wortman, J. L. , Bull. Am. Mus. Nat. Hist., vol. 4, 1892, pp. 135-144. 

 b Loomis, F. B., Am. Jour. Sci., 4th sen, vol. 23, 1907, pp. 35G-364. 



