1887] Mesozoic and Cenozoic of North America. 453 
WasaTcH.—Mammalia. Presence of Tæniodonta, Condy- 
larthra, and Pantodonta. Absence of Tillodonta, Dinocerata, 
Palæosyops, Hyrachyus, Amynodon, Achænodon, Triplopus, 
and suilline and selenodont Artiodactyla. 
This formation is characteristic of the region between the 
Rocky Mountains proper and the Wasatches, and has three 
principal areas. The most southern is in Northwestern New 
Mexico; the middle tract is in Southwestern Wyoming and 
Northeastern Utah ; the third tract is in Northwestern Wyoming, 
on the Big Horn River. 
Feet. 
Thickness in Northwestern New Mexico (Cope) 2500 
Thickness in Southwestern Wyoming ( Hayden) e 1500 
Thickness in Northwestern Wyoming (Wortman) 4000 
Winp River.s—Mammalia. Presence of Condylarthra, Tæ- 
niodonta, Pantodonta, Dinocerata, Palzosyops, and Hyrachyus. 
This fauna indicates the transition between the Wasatch and 
Bridger, since types are here associated which are elsewhere 
peculiar to the two horizons named. Thus, of the above zoolog- 
ical divisions the following are exclusively, Wasatch: Tænio- ` 
donta and Pantodonta. The remaining ones are Bridger, except- 
ing the Condylarthra, which probably occurs in beth Bridger 
and Wasatch. 
This formation is known from one area, which is on the head- 
waters of the Wind River, near the middle of Western Wyoming. 
The formation is, according to Hayden, not less than five thou- 
sand feet in thickness, 
Near the horizon of the Wind River beds must be placed the 
Green River Shales. This formation intervenes between the 
Wasatch and Bridger beds in Southwestern Wyoming, and differs 
entirely from both in lithological and palzontological characters. 
It consists of more or less finely-laminated calcareous or cal- 
ig oie ments: Be nave a depth of two thousand feet. 
been fine, indicating deep and still 
I 
2 = water. The Vertebrata obtained are almost exclusively fishes, 
two species of Crocodiles being the only exceptions. The fishes 
are clearly of Eocene character, and embrace some types (Gono- 
rhynchidz, Osteoglosside, and Chromididz) now restricted to 
the Southern Hemisphere faunæ.* Two of these types, together 
with two other genera of fishes, occur in the Bridger beds; and 
the two last named (Clastes and Pappichtlys) are also found in 
