ART. XIX.-REPORT ON THE GEOLOGY OF THE REGION OF 

 THE JUDITH RIVER, MONTANA, AND ON VERTEBRATE FOS- 

 SILS OBTAINED ON OR NEAR THE MISSOURI RIVER. 



By E. D. Cope. 



[Plates 30-34.] 

 LETTER OF TRANSMITTAL. 



Philadelphia, March 15, 1877. 



Sir : I send you herewith a synopsis of the results of an examination 

 of a portion of the region of the Upper Missouri, conducted by myself 

 during the past summer. The expedition was fitted out at Fort Benton, 

 and commenced geological work and collecting near the mouth of the 

 Judith River. The exploration was conducted eastward of this point, 

 on both sides of the Missouri, as far as Amell's Creek, 130 to 150 miles 

 east of Fort Benton, following the general course of the river. I after- 

 ward descended the Missouri by steamboat as far as Yankton, Dak., 

 and took advantage of many delays to examine the geology of the 

 neighborhood of its shores. The survey was much facilitated by the 

 accounts heretofore given by yourself of these regions, and I was able 

 to fully corroborate your observations. Especial attention was given to 

 the relations of the lignite beds of the Judith River and of localities 

 along the course of the Missouri, and some important additions to the 

 paleontology of the formation were made. To descriptions of these 

 fossils are added some accounts of species from the Niobrara Cretaceous 

 of Kansas. 



I am, very truly, yours, 



E. D. COPE. 



Dr. F. V. Hayden, 



United States Geologist-in-charge. 



1. — GEOLOGY OF THE JUDITH RIVER FORMATION. 



The formation through which the Missouri cuts its way from a short 

 distance east of Cow Island, for several hundred miles, is, as was orig- 

 inally pointed out by Dr. Uaydeu,* the Fort Pierre, or No. 4, division of 

 the Upper Cretaceous. Throughout this immense extent of territory, it 

 a[)pears as a soft bhu'kish or lead-colored shale, occasionally varied by 

 beds of soft sandstone and lignite. Some of the layers are saturated 



* Transactions Amer. Pbilos. Soc, ItiUO, p. 123. 



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