274 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



lenses. The sandstone, which is composed largely of 

 quartz sand in which fossils are rare, appears to have 

 been laid down by swift-flowing streams. The de- 

 posits of blue clay contain layers of lignite, ranging 

 from mere dark bands to rather thick beds, indicating 

 still water and a humid climate when vegetation was 

 accumulating rapidly. Skeletons of mammals found 

 in this blue clay were evidently swept into still-water 

 areas and covered with river sediment; but fossils are 

 rare in this stratum also. In many of the bands of 

 red clay, on the contrary, or at the contact of the red 

 and blue strata, great numbers of fragments of jaws 

 and scattered teeth are found. Such levels probably 

 represent parts of the basin floor as it was when these 

 creatures died. The beds of red clay, according to 

 Loomis, Granger, and Sinclair, were formed during the 

 drier cycles, when the carbonaceous matter of decaying 

 plants was completely oxidized, when iron compounds 

 were concentrated and oxidized, and when the bones of 

 animals exposed at the surface were weathered and 

 broken before they were entombed. These signs of the 

 alternation of moist and dry climate, indicated respec- 

 tively by blue and red clays, are not accompanied by 

 signs of excessive aridity, the mammals in the red and 

 blue clay bands being the same. Similar alternations 

 of red and blue clays are now found in the desert 

 basins of Asia. 



BIG HORN BASIN, WYOMING 



The discovery of Lamhdotlierium by the Amherst 

 College expedition of 1904 under Loomis and its 

 localization by the American Museum expedition of 

 1911 (Sinclair and Granger, 1911.1) in the uppermost 

 levels of the red-banded clay beneath the lignitic 

 beds of Tatman Mountain demonstrated the deposi- 

 tion of sediments of Wind River age in the Big Horn 

 Basin. The true Lambdoiherium zone is exposed on 

 all sides of Tatman Mountain and consists chiefly 

 of red-banded beds. Granger and Sinclair observe 

 (1912.1, p. 66) that the lower Eocene sediments of the 

 Big Horn Basin, like those of the Wind River Basin, 

 represent the filling in of a great trough surrounded 

 by mountains. No volcanic ash occurs. The moun- 

 tain streams have borne down gravel, sand, and clay 

 and deposited them in stream channels or spread 

 them over flood plains. No evidence of wind trans- 

 portation has been observed. The red and blue 

 banding of the clays occurs in more or less regular 

 alternation. 



BEAVER DIVIDE, WYOMING 



The discovery of a typical Wind River fauna on 

 Beaver Divide by Olsen, of the American Museum 

 party of 1910, was a most important one, because it 

 extends the range of this fauna many miles to the 

 southwest. The entire fauna was obtained at or near 

 a certain stratum of bluish-green shale resting on a 

 band of red shale, the fossiliferous zone not exceeding 

 10 feet in thickness. (See Chap. II.) Remains of 

 the animals listed below were obtained: 



Equidae: 



Eohippus craspedotus. 



Eohippus? venticolus. 

 Lophiodontidae : 



Heptodon calciculus. 



Heptodon ventorum. 



Heptodon n. sp. 

 Titanotheriidae : 



Lambdotherium popoagi- 

 cum. 

 Amblypoda: 



Coryphodon sp. 



Reptilia: 



Glyptosaurus (scutes). 



Crocodile (scutes, verte- 

 brae, and teeth). 



Turtles (numerous frag- 

 ments) . 

 Insectivora: 



Hyopsodus n. sp. 



Hyopsodus sp. 

 Creodonta: 



Didymictis? altidens. 

 Primates: 



Microsyops sp. 



The fish and aquatic reptiles in this fauna indicate 

 plainly that the deposit on Beaver Divide was fluvia- 

 tile, and, as Granger and Sinclair observe, go far toward 

 establishing the theory that the Wind River shales 

 were flood-plain deposits, a theory that is further 

 supported by the presence of numerous channel 

 fillings of coarse sandstone. All the fossils from the 

 shales are fragmentary and consist mostly of teeth 

 whose roots are worn off, indicative of water trans- 

 portation and abrasion. 



HUERFANO BASIN, COLORADO 



The Lambdotherium zone was discovered in Colo- 

 rado by Dr. J. L. Wortman while he accompanied 

 the writer in 1897 (Osborn, 1897.126) on a survey of 

 the Huerfano Eocene deposits, which were first 

 announced by Hills in 1888 (Hills, 1888.1). The 

 zoogeographic significance of this discovery is evident 

 from the fact that it carries the Lambdoiherium 

 fauna eastward to the foothills of the Rocky Moun- 

 tains, between the famous extinct volcanoes known as 

 the Spanish Peaks. 



Wortman described these beds as follows: 

 These beds of the lower division [Lambdoiherium zone] are 

 indistinguishable, so far as their general appearance and litho- 

 logical characters are concerned, from those of the upper level 

 [Palaeosyops fonlinalis zone]. The fossils occur apparently 

 in a single stratum not exceeding 10 or 15 feet in thickness and 

 not more than 30 or 40 feet from the base of the formation. 

 They underlie the beds of the upper division with perfect 

 conformity, and there is at present no means of determining 

 exactly where the one ends and the other begins. That 

 sedimentation was continuous and iminterrupted from the 

 beginning to the close of the whole [Huerfano] deposit, I do 

 not think there can be the slightest question. The exact 

 locality from which the greater number of the fossils of the 

 lower beds were obtained is Garcias Caiion, about IJ-^ miles 

 south of Talpa or the mouth of Turkey Creek. [Osborn, 

 1897.126, pp. 253-254.] 



The animals associated with Lambdotherium in this 

 zone are provisionally identified by Osborn and 

 Matthew as follows: 



Titanotheriidae Lambdotherium popoagi- 



cum. 

 Creodonta Didymictis altidens. 



Didymictis leptomylus. 



Oxyaena lupina. 



Insectivora Hyopsodus sp. 



Amblypoda Coryphodon ventanus. 



Artiod actyla Trigonolestes secans. 



