366 The American Naturalist. “ [Age 
present its limits are undetermined. The bituminous shales of the 
Colorado group, which are evidently the source of the oil, underlie a — 
wide belt of country along the eastern base of the Rocky Mountains, _ 
Along this zone, intermediate between the mountains and plains, oil _ 
fields will probably be found in places where the shales have been — 
somewhat affected by the proximity of the crystalline rocks, and yet 
have not been too much disturbed and broken. (Prof. J. S. Newberry, 
School of Mines Quart, Vol. X., January, 1889.)—-In a recent — 
paper, Prof. Angelo Heilprin has presented the leading facts touching — 
the geological and paleontological relations of the Cretaceous deposits 
of Mexico. These deposits cover, or are scattered over, the greatest 
part of Mexico, from the Rio Grande to (or through) the states of — 
Colima, Michoacan, Guerero, and Oaxaca. (Proc. Acad, Nat. Sciences, 
Phila., Dec., 1890.) p 
Cenozoic.—R. Lydekker has collected circumstantial evidence 
which justifies him in regarding the so-called genus Sceparnodon as 
based upon the upper incisors of the gigantic wombat known as Phas- 
colonus. (Proc. Roy. Soc., Vol. 49.)——-Mr. George Becker has 
published new evidence in favor of the authenticity of the Calaveras 
skull, and amply sufficient of itself to prove that man existed during 
the auriferous gravel period in California. He has the sworn state- 
