14 



Sellards — Comanchean Formation. 



obtained from some of the wells, together with the often 

 imperfect preservation of the fossils, the minimum depth 

 to the top surface of the Comanchean formations is fre- 



FiG. 1. Sketch map indicating location of wells. 



quently difficult to determine. Nevertheless, approxi- 

 mate results are obtained by indicating the depth at which 

 fossils of these formations are first recognized. In the 



