92 Cretaceous. 



quent recession of the salt and brackish water, took place during- the 

 deposition of this group. 



Prof Ha3^den proposed to call the strata found in the Judith basin 

 near the sources of the Missouri river, consisting of ancient lake de- 

 posits, and not differing materially from those of the Fort Union Group, 

 the Judith Group. It contains impure beds of lignite, fresh-water 

 mollusca, a few leaves of deciduous trees and a great number and 

 variety of reptilian remains. 



There is no real phj'sical break in tlie deposition of the sediments 

 between the well-marked Cretaceous and Tertiary strata. In some 

 localities the continuity is clear and beautiful in the highest degree. 

 On Green river, and in the Bitter Creek Valley, one can trace the 

 continuity step by- step, so far as the strata are concerned, from the 

 Cretaceous through the greatest thickness of clays, sands, and sand- 

 stones of the Lower Tertiar}^ to the purely fresh water beds of Green 

 river shales,- Washakie, or Bridger Groups. In these localities the 

 influence of the elevation of the mountain ranges has been such as to 

 expose the outcroping edges of all the strata, from the Cretaceous to the 

 sands of the most recent Tertiary, like the leaves of a book. In the 

 clays interspersed among the coal beds, in the Bitter Creek valley, 

 several species of oyster shells occur in seams. At Bear river, we 

 have well defined Cretaceous strata and from these we ascend, through 

 a series of sandstones and clays, with an abundance of shells of the 

 genus Ostrea and a few other marine forms, resembling Tertiary types 

 as much as Cretaceous. Soon we come to the coal-beds, which at 

 this localitj' are nearly vertical. Above them we find seams of 03^ster 

 shells, but no other marine forms. And finally, high up in the upper 

 beds of the coal group, we find the greatest profusion of brackish and 

 fresh water life. The coal group in Weber Valley, and at Coalville 

 is referred to the Cretaceous. 



Prof. F. B. Meek* said that some of the specimens from near 

 Bear river, and at Coalville, Utah, from a light-colored sandstone 

 containing beds of a good quality of brown coal, appear to belong to 

 a member of the Cretaceous series not corresponding to any of 

 those named in the Upper Missouri countr}-; though it is, as he 

 believed, represented by a similar sandstone under the oldest estuary 

 Tertiar}' beds at the mouth of the Judith river, on the Upper Mis- 

 souri. In 1860, Colonel Simpson brought from this rock, on Sulphur 

 Creek, a small tributary of Bear river, in Utah, some casts of In- 



'■'■ Hayden's U. S. Geo Suv. of Wyoming, etc. 



