THE EOCENE OF NORTH AMERICA 455 



the "Amyzon Group" {American Naturalist, June 1880), with 

 the shales of Osino and of the South Park of Colorado." 1 The 

 Amyzon beds of Nevada appear in the accompanying map. 

 Those of Colorado and of Oregon are not here mapped. 



THE MANTI FORMATION 



Cope has described this formation as follows: 2 "There is, 

 however, a series of calcareous and silico-calcareous beds in cen- 

 tral Utah, in Sevier and San Pete counties, which contain the 

 remains of different species of vertebrates than those which have 

 been derived from either the Green River or Amyzon beds. 

 These are Crocodiltis, sp., Clastes cuneatus Cope, and a fish pro- 

 visionally referred to Priscacara under the name P. testudinaria 

 Cope. There is nothing to determine to which of the Eocenes 

 this formation should be referred, but it is tolerably certain that 

 it is to be distinguished from the Amyzon beds. In its petro- 

 graphic characters it is most like the Green River, as it consists 

 in large part of shales. The laminae are generally thicker than 

 those of Green and Bear rivers. The genera Crocodiltis and 

 Clastes have not been found heretofore in Green River beds, 

 although they are abundant in the formations deposited before 

 and after that period. Until its proper position can be ascer- 

 tained, I propose to call the formation the Manti beds." 



Some years later Cope regarded these beds as of probably 

 Wind River age. He says, "A probable second locality of this 

 [Wind River] formation is known in eastern Utah, in the Was- 

 atch Mountains. This formation is known as the Manti beds." 3 



THE MOJAVE FORMATION 



Fairbanks has described 4 a formation in southeastern Cali- 

 fornia which is probably Eocene. "On the northern slope of 

 the El Paso range, between Mojave and Owen's Lake, there is a 

 series of beds of clays, sandstone, volcanic tuffs, and interbedded 



1 Proc. Amer. Philos, Soc, Vol. XIX, p. 61, 1880. 



2 Amer. Nat., Vol. XIV, pp. 303, 304, 1880. 

 *Ibid., Vol. XXI, p. 454, 1887. 



4 Geology of eastern California, Am. Geol., Vol. XVII, p. 63, 1896. 



