BY Ta aN 
OF THE 
AMERICAN MUSEUM OF NaTuRAL History. 
VOLUME XK KLV 4046) 
56.9.743 (1181:78.7) 
Article I— A REVISION OF THE LOWER EOCENE WASATCH 
AND WIND RIVER FAUNAS. 
By W. D. MatrHew and Wa.LterR GRANGER. 
Introduction. 
In 1891 the Department of Mammalian Paleontology of this Museum 
was founded by Professor Henry Fairfield Osborn. The first expedition for 
fossil mammals was sent out in charge of Dr. J. L. Wortman to the Lower 
Eocene Wasatch formation of the Big Horn Basin, Wyoming. The results 
of this auspicious beginning of the Museum’s fossil-hunting expeditions 
were described in the ‘Bulletin’ for 1892, volume IV. Another very suc- 
cessful expedition was conducted by Dr. Wortman the next year into the 
Paleocene (Puerco) of New Mexico. In 1895 the Museum purchased the 
Cope Collection of North American Fossil Mammals, including the Eocene 
and Paleocene collections obtained by Professor Cope and his assistants 
and described and figured in ‘Tertiary Vertebrata.’ Expeditions in charge 
of Dr. Wortman in 1893-96 added largely to the Eocene collections thus 
brought together. In 1903 Mr. Walter Granger began a systematic and 
thorough search of the Middle and Lower Eocene and Paleocene formations 
of Wyoming and New Mexico which has continued for ten years with great 
suCCESS. 
The thorough stratigraphic studies made by these expeditions and 
exact records of level and locality of every specimen, have made it possible 
to correlate the faunas and trace the evolution of the various races much 
more precisely and certainly. The great amount of new material, and more 
complete specimens of rare and little known species have as yet been de- 
scribed only in small part. 
The present revision is concerned with the Lower Eocene faunee, the 
