AMERICAN 477 



the almost incredible thickness of 10,000 to 20,000 feet has been 

 reported. No less than six distinct, successive marine faunas are 

 found in the Comanche limestones of Texas, and the faunal rela- 

 tionships of this region are closest with the Mediterranean province 

 of Europe, and especially with the Lower Cretaceous of Portugal. 



In the northern interior region the Lower Cretaceous beds were 

 all laid down in inland bodies of water, part of which, at least, 

 were fresh. One such body of water covered southern Wyoming, 

 extending down the eastern flank of the Rocky Mountains into 

 Colorado. In it were deposited a thin mass of sands and clays, 

 the Como Beds} in which are preserved the remains of a rich land 

 fauna of reptiles and mammals. These beds are usually referred 

 to the summit of the Jurassic, but their near equivalence seems to 

 be with the Trinity of Texas, the basal Potomac of the Atlantic 

 border, and with the English Wealden, all of which are well-nigh 

 universally regarded as Cretaceous. Another non-marine and, at 

 least locally, fresh body of water occurred east of the Gold Range 

 of British Columbia, extending southward into Montana, and in it 

 were deposited the sands and clays of the Kootanie stage, the 

 plant remains of which correlate it with the lower Potomac, though 

 it may have been considerably later than the Como beds. In this 

 northern area there is no evidence of deep water, but only of 

 shallow seas or lakes, with tracts of low-lying, swampy lands, on 

 which a luxuriant vegetation produced valuable deposits of coal. 

 Other inland . waters occupied an unknown extent of the Great 

 Plains area ; Lower Cretaceous beds have been found surrounding 

 the Black Hills and in a few other localities. 



Along the Pacific coast Lower Cretaceous rocks are displayed 

 on a great scale. The Great Basin land then extended from 

 southern Nevada to latitude 54° N. in British Columbia, with the 

 Sierra Nevada rising along part of its western shore, to which the 

 Pacific extended. North of the Gold Range in British Columbia, 

 the ocean spread eastward, though no doubt broken by many 



1 These beds were named by their describer, Professor Marsh, the Atlantosaurus 

 Beds, but as this name is inadmissible, the term Como Stage may be substituted, 

 from Como, Wyoming, the typical locality. 



