PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 

 The 318th meeting was held at the Cosmos Club, March 28, 1917. 



INFORMAL COMMUNICATIONS 



C. J. Hares: Gastroliths in the Cloverly formation. Gastroliths were 

 found in the summer o 1916 in the Cloverly formation in the northeast 

 portion of the Bighorn Basin, Wyoming, at about the base of Pryor 

 Mountains in Montana. These gastroliths occur in the shale portion 

 of the Cloverly, between the Pryor conglomerate member at the base 

 and the Greybull sandstone member. The gastroliths occur in such 

 large quantities and so large individually that I was led to question 

 the theory that they were polished in the stomachs of dinosaurs and 

 plesiosaurs, as advocated by Williston and others. The shale, however, 

 does carry some bones of these animals. A large representative col- 

 lection was made; some of the specimens are very highly polished, and 

 others polished scarcely at all. But if the highly polished ones are true 

 gastroliths, then it is probable that the unpolished ones are likewise 

 gastroliths. Some of the stones are over 6 inches long. The material 

 consists mostly of highly siliceous rocks, jasper, chalcedony, quartzite, 

 etc. 



Discussion: C. W. Gilmore spoke of the definite association of 

 similar stones with single skeletons of plesiosaurs. 



REGULAR PROGRAM 



C. J. Hares: The southern extension of the Eagle sandstone and its 

 relation to the Niobrara shale in Wyoming. In the summer of 1916, 

 while mapping the Elk Basin and Byron oil fields and an area extending 

 from Bridger, Montana, to Greybull, Wyoming, detailed stratigraphic 

 information was obtained, showing the correlation of the Upper Cre- 

 taceous formations of Montana with those of Wyoming. The classic 

 Cretaceous section of Montana, as worked out by Hayden, Weed, 

 Stanton, and Hatcher, along the Musselshell River, has been carried 

 southward by the detailed work of Lloyd, Bowen, and Hancock to the 

 Yellowstone River. The formations so mapped include the Colorado 

 shale, the Eagle sandstone, Claggett shale, Judith River formation, and 

 Bearpaw shale. The upper part of the Eagle and the Judith River 

 are mostly of fresh water origin, the others in the main are marine. 



429 





