MESOZOTC. 267 
the Cenozoic series, but further reflection induced rae to place 
it as now arranged. The reason is as follows : Although Pla- 
cental Mammalia are not now known otherwise from Mesozoic 
beds, the other forms of the Puerco are especially Mesozoic in 
character. Such are the Choristodere Reptilia and the Multitu- 
berculate Marsupial ia, neither of Avhich occur above, while both 
occur below the Puerco, the Multituberculata down to the 
Trias inclusive. Then the Placentialia are entirely peculiar in the 
absence of the Diplarthra and of the Rodentia, orders always 
found in the Cenozoic beds. Then the characters of the Con- 
dylarthra and Amblypoda and many of the Creodonta, which 
represent Tertiary types, are so peculiar that we are led to sus- 
pect that when the Cretacic Mammalia are fully known they 
cannot differ very widely from those of the Puerco. 
But one area of this formation is definitely known ; this is in 
Northwestern New Mexico and Southwestern Colorado. It con- 
sists of sandstones and soapy marls, and has a thickness of eight 
hundred and fifty feet. It is immediately overlaid by the 
Wasatch Eocene, and rests on the Laramie. 
Total thickness of the Mesozoic system (greatest): 
Feet. 
Triassic, 16,000 
Jurassic, 6,000 
Cretacic, 4,900 
Postcretacic, 5,850 
32,750 
NOTE ON THE MESOZOIC SYSTEMS. 
The Report on the Geology of the Uinta mountains having 
been published in 1876, according to the date on the title-page, 
while the vols. i. and ii. of King's Report on the Geology of the 
Fortieth Parallel were not published until 1878 and 1877 respec- 
tively, it becomes necessary to examine whether any of the names 
used b^ the latter author are antedated by any of those of 
Powell. The Mesozoic sands below the Cretacic given by Powell 
are the following, in descending order. They are all referred 
(p. 41) to the Jura-Trias system. 
Flaming Gorge 1200 feet 
White Cliff; 1100 " 
Vermilion Cliff; 1100 " 
Shinarump, 1800 " 
