Art. VIII.— On the Vertebrata of the Wind River 

 Eoeene Beds of Wyoming^. 



By £. D. Cope. 



The Wind Eiver, the principal source of the Big Horn, rises in the 

 Wind Eiver Mountains, in Western Central Wyoming, and flows through 

 a bad-land region for a hundred miles. This region was explored by 

 Dr. F. V. Hayden in 1858, who makes the following observations re- 

 specting it (American Naturalist, 1878, j). 831) : 



Along the east side of the Wind River Mountains, and filling up the Upper Wind 

 River Valley, is a great thickness of Tertiary strata that has been weathered into 

 very remarkable forms, and which are known in the West as "bad lands". The 

 strata are most beautifully variegated with various shades of pink or brick-red color, 

 so that they sometimes remind one of the Jura-Trias red beds. This formation was 

 described by me in 1859 in detail, and named the Wind River group. It covers a 

 broad area in this region, extending from the source of Wind River to the Sweet 

 Water Mountains, south, more than one hundred miles, and west an average width of 

 one to five miles. The aggregate thickness of this group cannot be less than 5,000 

 feet. On the west side of the Wind River Mountains no formations older than the 

 Wasatch group are found. This group rests, doubtless, on the Archsean nucleus, in- 

 clining at the base 5 to 10 degrees. All the older sedimentary rocks have been entirely 

 swept away from the granites for a distance of 100 miles ; while on the opposite or 

 east side, all the corresponding strata are visible, from the Silurian to the Cretaceous 

 The Wasatch beds cover a large part of the Green River Valley, esj)ecially about its 

 sources. 



During the past summer I sent a party into the Wind Eiver Basin, 

 under direction of Mr. J. L. Wortman, already well known from his 

 numerous important i^aleontological discoveries in Oregon. This gen- 

 tleman made a thorough exjiloration of the bad lands, and probably ob- 

 tained all the fossils found on the surface in the region. The following 

 list of forty-five species shows that the collection embraces nearly all of 

 the characteristic types of the American Eocene, and that tweutj'-six 

 species are aew to science. Among the most remarkable of these I 

 may cite the large flesh-eater Protopsalis tigrinus, the largest of the 

 Eocene period yet known, and the Amblypod, Batlujopsts Jissidens, an 

 important addition to the forms of that peculiar order. 



Mr. Wortman's explorations were not accomplished without accident, 

 he having lost most of his outfit on his first crossing of the Wind Eiver. 

 The bad lands form a most forbidding region, mostly waterless, and at 

 an elevation which is Rnfavorable to the sparse vegetation which is 

 permitted by the dryness of the climate. 



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