OF WESTERN NORTH AMERICA. 



47 



Bridger genus known which could be directly descended from the 

 species L. popoagicum. 



Of Ungulata-Artiodactyla Trigonolestes survives from the Wasatch. 



WIND RIVER a; LAMBDOTHERIUM ZONE. 



Period of lower deposition, — ^Wortman" concluded on liis second 

 visit (1891) that the lower Wind River is absolutely distinct from 

 the Wasatch of the Bighorn Basin and belongs to a succeeding depo- 

 sition. He supposed that the Wind River country was above water 

 during the laying down of the Wasatch sediments^ and that some 

 time after the close of the Wasatch a lake was formed on the site of 

 the present Wind River basin. Loomis^ (1907) regards the Wind 

 River formation as epicontinental, fluviatile, and flood-plain, like the 

 Wasatch, and sHghtly subsequent in the beginning of its deposition. 



General characters. — A total thickness of 400 to 500 feet near the 

 sources of Wind River. Readily distinguished geologically by hori- 

 zontally alternating bands of bright-red and gray fossil-bearing shales 

 and sandstones containing CorypTiodon, turtles (Trionyx), crocodiles 

 (Crocodilus) , Lacertilia-Anguidse (Gly ptosaurus) , etc. The conglomer- 

 ates, indicating rapid stream or river invasions, are barren. The 

 writer is indebted to Professor Loomis for the section (fig. 5, p. 44) 

 and for his observations on stratigraphic distribution. 



Fauna. — The chief part of the Wind River fauna listed above is 

 from these red beds. In the lower red beds are found CorypJiodon, 

 EoJiippus, Lamhdotlierium, and several species of Hyopsodus; among 

 primates, Notharctus and Pelycodus. The American Museum collec- 

 tions of 1905, nearly all from the red beds, exhibit a closer degree of 

 affinity to those of the upper Wasatch than is found in specimens 

 from the upper beds. The Amherst collections include from these 

 beds BatJiyopsis, the earliest known member of the Dinocerata. 



WIND RIVER B; BATHYOPSIS ZONE. 



Period of upper deposition. — The upper levels, or Wind River B, 

 are naturally to be compared with Bridger A, but unfortunately too 

 few fossils have as yet been found to afford such a basis of correlation. 



Hay den (1869) described these beds as consisting of 800 to 900 feet 

 of ferruginous, coacse-grained sandstones, alternations of sandstones 

 and marls, light sandstones, friable sandstones, and indurated marls. 

 They are probably in large part of volcanic-dust origin. Some of 

 these strata indicate great disturbances in the water during their 



a Wortman, J. L., Fossil mammals of the Wasatch and Wind River beds: Bull. Am. Mus. Nat. Hist., 

 vol. 4, 1892, pp. 143-144. 



Loomis F. B , Origin of the Wasatch deposits: Am. Jour. Sci., 4th ser., vol. 23, 1907, pp. 356-364. 



