130 



THE AGE OF MAMMALS 



intermediate grayish 'shales,' as well as the coarse conglomerate beds 

 formed by rapid stream action of river invasions, are barren. 



Even in the 'red beds' fossils are scarce except in one or two very limited 

 areas, and as a rule fragmentary and imperfectly preserved. The only 

 complete skeleton recorded is the type of the famous Eohippus venticolus, 



Newly 

 Arriving 

 Mammals 



In;. |_'. I III' Lower l-iid'ciii- JKiiiilcil layii,^ <.l 1 1 ii- Wind River Badlands, basin of the 

 "Wind River, Wyo. Zone of Latnhdothcrium and of the last stages of Coryphodon. Photo- 

 graph by American Museum of Natural History, 1896. 



found by Wortman in 1880. It has required years of the most arduous 

 search, concluding with the ' microscoping ' of the beds by the American 

 Museum party of 1909, to round out materials for our knowledge of this, 

 including the discovery of the skulls of two of the most characteristic forms. 

 Faunal life. — With the Wind River we enter a 

 new life zone, signalized by the earliest record of a 

 new and very important family of perissodactyls, the 

 titanotheres, which is represented by the genus Lamb- 

 dotherium from which the zone takes its name. 

 Accompanying this small, light-limbed and very 

 abundant titanothere is the larger titanothere known 

 as Eotitanops, a form truly ancestral to the great 

 titanotheres of Eocene and Oligocene times. There 

 are many other newly arriving mammals, including 

 twelve new genera and fifty-five species, which have 

 not been found in the Wasatch. Nine of these new 

 genera of mammals are also found in the Bridger. 

 Wind River life is thus transitional and prophetic of 

 Bridger life. The Wind River, however, represents 



Titanotheres 



Lambdotherium 



Eotitanops 

 Hyracodonts 



Hyrachyus 

 Uintatheres 



Bathyopsis 

 Primates 



Nothardus 



Washakius 



Microsyops 



