A SAUROPOD DINOSAUR IN OKLAHOMA 



97 



formation dips under other Cretaceous formations to the south and 

 along Red River forms the reservoir of numerous artesian wells. 



The thickness of the Trinity in Oklahoma varies from 200 to 800 

 feet. 



The formation rests unconformably upon granites and Paleozoic 

 rocks. It consists of conglomerates, unindurated or friable sandstones 

 and clays mixed with varying quantities of sand. Most of this mate- 

 rial bears evidence of being derived from adjoining rocks which formed 

 the shore of the Cretaceous Sea. The conglomerates especially bear 

 this characteristic. They always occur near the base of the formation 

 and are formed of waterworn bowlders and pebbles of the rocks 



Fig. 4. — Right coracold of sauropod, posterior border; one-fourth natural size. 



upon which they rest, or of a formation near at hand. The sands 

 and clays are not continuous over large areas but consist for the 

 most part of lentils which are cross-bedded and irregularly thrown 

 together. Everything points toward deposition in shallow turbulent 

 water. 



A following section across the Trinity along the line of the 

 Missouri, Kansas and Texas Railroad from near Caddo, Oklahoma, 

 to near Atoka, will give the reader some idea of the character of the 

 Trinity at this place, and of the stratigraphic relations of the forma- 

 tions in which the bone was found. 



The writer found the fossil dinosaur bone herewith figured in 

 August, 1908, while making an examination of that region under the 

 direction of the Oklahoma Geological Survey. 



