STRATIGRAPHIC POSITION OF JUDITH RIVER FORMATION 533 
zoic time having been found there and identified by fossils.”” The 
three members referred to were No. 4, Fort Pierre, No. 5, Fox 
Hills, and No. 6, Fort Union. The thickness of the latter was 
estimated at 400 feet, and the strata are described as beds of white 
sandstone containing occasional layers of a clayey brown sand 
rock, ‘‘at the mouth of the Judith River, evidently overlying the 
beds of No. 5 [Fox Hills] before referred to.” From these beds 
they obtained the vertebrae and long neck bones of dinosaurs 
identified by Professor Marsh as belonging very near the genus 
Hadrosaurus |Trachodon| of Leidy. With these remains were 
found Unios and, in some layers, a little lignite, the general associa- 
tion seeming to refer the deposits to the Fort Union beds. 
Professor E. D. Cope was the next to visit the region. In the 
summer of 1876 he explored the region near the mouth of the 
Judith River and eastward as far as Armel’s Creek, 130 to 150 
miles to the eastward from Fort Benton. He fully corroborated 
Hayden’s observations and his sections are substantially the same. 
He regarded the Judith River beds as Cretaceous, with Tertiary 
affinities, and referring to their position, says? ‘In the Judith 
region the relation of the Fox Hills sandstone to the superincum- 
bent strata is everywhere observable.” ‘‘The ferruginous, soft 
sandstone of the Fox Hills group is everywhere the line of demarka- 
tion between the black shales of No. 4 [Fort Pierre] below and the 
Judith River beds above.’’’ 
The last identification of fossils made by Professor F. B. Meek 
was for Professor Cope. The fossils were Inoceramus barabint, 
Inoceramus sp.; and Baculites compressus, and were obtained by 
Cope’ from the black shales of No. 4. Although Meek had not 
revisited this region, his last word on the Judith River beds is in- 
teresting and illuminating.’ Basing his opinion upon the inverte- 
brates found in the beds immediately underlying the Judith River 
beds near the mouth of the Judith River, he correlates them with 
the upper part of the Fox Hills.6 As to the Judith River group, 
t Bull. U.S. Geol. and Geog. Surv., III (1877), 569. 
2 Tbid., p. 568. 3 Ibid. 4 [bid. 
5 Report of U.S. Geol. Surv. Terr., UX (1876). 
6 Tbid., p. XXXVi. 
