118 GEOLOGY. 



ward around the western end of the Ouachita Mountains, an undeter- 

 mined distance into Kansas. 1 Though they appear at the surface in 

 small areas only, their extent may be considerable beneath younger 

 formations. The exact relations of the Comanchean strata of Kansas 

 {Cheyenne sandstone, Kiowa shale, etc.) to those of Texas have not 

 been established. The Kansas beds appear to be referable mainly 

 to the Washita epoch, though some of them may be older. The aggre 

 gate thickness of the Kansas beds is less than 200 feet. The Coman 

 chean system also occurs in Oklahoma (near Garrett) and Colorado 

 (near Canyon City). 2 



In Mexico. — As in Texas, the Comanchean system of Mexico is 

 mainly limestone, and, though but imperfectly known, it has been 

 estimated to have the extraordinary thickness of 10,000 to 20,000 feet. 

 While the system in Mexico agrees with that of Texas in its large pro- 

 portion of calcareous rock, the soft chalk of the plains grades into 

 hard limestone in the mountains. This difference is perhaps the result 

 of the dynamic movements to which the Mexican strata have been 

 subject. 



The distribution and character of the Comanchean system in Mexico 

 are such as to show that a large part of that country was beneath the 

 sea. It has been conjectured that the waters of the Atlantic and 

 Pacific mingled over the site of some part of the present land, but this 

 has not been proven. If there was union, it was probably across 

 southern Mexico or perhaps even Central America, and so related, 

 by shallow water restriction or by ocean currents, to the Californian 

 coast, as to prevent free faunal inter migration. 



In its abundance of limestone, the series of Texas and Mexico 

 resemble the Lower Cretaceous of the northern part of South America, 

 and southern Europe. It is a notable fact also, that the faunal affini- 

 ties of the Comanchean system are with South America and Europe, 

 rather than with California, where marine Lower Cretaceous strata 

 are known. 



1 For summary of the Lower Cretaceous of Kansas, see Prosser, " Comanchean 

 Series of Kansas," the Univ. Geol. Surv. of Kans., Vol. II, 1897. This volume gives 

 bibliography of the Lower Cretaceous of the state. See also Hill, Am. Jour. Sci., Vol. 

 I, 1895, and Bull. Geol. Soc. Am., Ill, p. 85; Gould, Am. Geol, Vol. XXV, pp 

 10-40; and Cragin, Am. Geol., Vol. VI, pp. 233-8. 



2 Stanton, Jour. Geol., Vol. XIII, p. 657. 



