Chapter I. 



DESCRIPTION OF THE VERTEBRATE-BEARING BEDS OF NORTH-CENTRAL 



NEW MEXICO. 



S. W. WiLLISTON AND E. C. CASE. 



The following description of the Permo-Carboniferous beds of New Mexico 

 is a portion of a more extended article by the authors in the Journal of Geology, 

 only such portions being repeated as bear upon the character of the beds and indi- 

 cate the conditions under which the animals lived and were preserved.* 



The regions explored were El Cobre Caiion, north of Abiquiu, and the expos- 

 ures in the walls of the Puerco and GalUna Rivers, all in Rio Arriba County. 



I07°00' 



10 Miles 



Fig. I. — Map of the Mesa Prieta and adjoining country. Fossiliferous Permo-Carboniferous areas shown 

 by shading. Comparison with the Gallina topographic sheet will make details clear. 



El Cobre Canon or basin is formed by the erosion of an unsymmetrical dome- 

 shaped anticline, more or less faulted on the northeastern and southeastern sides, 

 the brim formed everywhere by the massive sandstones of basal Upper Triassic 

 age, the strata sloping in all directions, but chiefly east and west. The basin thus 



* The Permo-Carboniferous of northern New Mexico. Journal of Geology, vol. xx, No. i, pp. 1-12., 



I 



