250 STANTON 



The same dinosaur horizon occurs on the Missouri River a few miles 

 north of the mouth of the Cannonball River, where in 1908 1 collected 

 bones identified as Ceratopsia and Trachodon from soft sandstones 

 and shales approximately 100 feet above the top of the Fox Hills sand- 

 stone, which is here fossiliferous and has its most northern outcrop on 

 the west side of the Missouri near old Fort Rice, about 25 miles south- 

 east of Mandan, North Dakota. The fossil plants listed by Knowlton 

 from my collection were obtained from beds a few feet above the 

 highest observed dinosaur bones. 



There is doubtless a continuous area of dinosaur-bearing beds 

 extending through northern South Dakota and southern North 

 Dakota between the Alissouri and Little Missouri rivers. Unpub- 

 lished records furnished by Prof. J. E. Todd, former State Geologist 

 of South Dakota, show localities for Triceratops and also for a number 

 of brackish-water invertebrates in the region of Grand and Moreau 

 rivers. The shells include Anomia, Ostrea glabra, Corhicula suhel- 

 li plica, C. cytherifonnis, and C.occidentalis. Dinosaurs and brackish- 

 water shells were also obtained in this region by F. V. Hayden on one 

 of his early expeditions. 



These beds immediately overlying the Fox Hills along the Missouri 

 in North and South Dakota might fairly be regarded as the basal 

 part of the Fort Union formation, since it is the first named formation 

 above the Fox Hills in the section, if it were not for the fact that 

 Meek and Hayden limited the type section of that formation to the 

 exposures along the Missouri from Fort Union to Fort Clark and 

 up the Yellowstone into Montana, while these lower beds in question 

 occur along the Missovi below Fort Clark. When the Fort Union 

 formation was named by Meek and Hayden'"' they said it 



occupies the whole country around Fort Union [near the mouth of 

 the Yellowstone] extending north into the British possessions, to 

 unknown distances, also southward to Fort Clark. Seen under the 

 White River group on North Platte River above Fort Laramie. Also 

 on west side Wind River Mountains. 



In later publications both Meek and Hayden treated these lower 

 beds as probably distinct from the Fort Union. Thus Meek'^ says: 



'^ Proc. Acad. Nat. Sci. Phila., 1861, p. 433. 



'«U. S. Geol. Surv. Terr., Vol. IX, 1876, p. XLIX. 



