Geology and Paleontology. 161 
e researches of General Tillo on temperature have led him 
to conclude that the continents are, as a whole, 3° cent. colder than 
the oceans. between the latitudes of 90° N. and 50° S. The New 
Continent is 3° colder than the Old; and the Atlantic 2.6° 
colder than the Pacific. The northern hemisphere contains 14 per 
cent. of the cold regions, 35 per cent. of temperate, and 51 per cent. of 
hot regions. Dr. Supan’s estimate, reached by a different method, 
gave 15, 32 and 53 per cent. for these regions. 
GEOLOGY AND PALZONTOLOGY. 
THE VERTEBRATE FAUNA OF THE PuERCO Epocu.—I have 
recently revised my material representing this fauna, and have 
added eighteen species to those already known. One of these belong 
to a new genus, viz.: Onychodectes, allied to Conoryctes (Creodont). 
The Puerco formation lies on the Laramie in North Western 
New Mexico and South Western Colorado, and is largely covered 
by the Wasatch Eocene in both regions. It was discovered by 
the writer in 1874, at its eastern outcrop of about 500 feet thick- 
ness, and was identified by Endlich and Holmes in Colorado, in 
1876, where the thickness reaches 1000 to 1200 feet. On the San 
Juan river, its thickness is 700 feet, while at its western outcrop, 
south of that river, its thickness is 800 or 900 feet. While the 
formation possesses lithological peculiarities, no clue to its impor- 
tance in geologic chronology was known until the discovery of 
vertebrate remains was made in 1880, by Mr. David Baldwin. 
With the evidence derived from this material the writer has been 
able to interject into the series of epochs of geological time a period 
which must have possessed many peculiarities, and which differed 
in such important essentials from those which preceded and from 
those that followed it, that an immense interval between them is 
proved to have existed, such as had not been previously suspected. 
The rich fauna which it contains displays characters which indicate 
others yet to be discovered before connections with other epochs both 
prior and subsequent can be known. 
The vertebrate fauna includes up to the present date one hun- 
dred and six known species. Four species of Mollusca have been 
discovered, which have been determined by Dr. C. A. White, of, 
the U. S. National Museum. They are Unio rectoides White; 
Helix adipis White; H. nacimientensis White, and Pupa leidyi 
Meek. The first named is found in the Wasatch, and the last in 
the Laramie; the two other species are peculiar. Besides these; 
the only other indications of organic life at that period is petrified 
_ Wood of undetermined trees, which is quite abil : 
