Douglass : A Geological Reconnaissance. 279 



the Frying Pan Basin northwest of Dillon, and from there northward 

 beyond Glendale in the Bighole Valley north of Dillon, and (5) on 

 the Hell Gate River from Garrison to Druramond, besides innumer- 

 able other smaller exposures. On the Atlas Folios of the U. S. Geolog- 

 ical Survey the strata have been mapped as Dakota and Montana-Col- 

 orado. Some of the best exposed, and apparently the most persistent 

 and widely distributed Cretaceous rocks, are the laminated and thick- 

 bedded limestones which every\vhere contain multitudes of fresh- 

 water mollusca, especially gasteropods. These usually occur near the 

 bottom of the Cretaceous series and have been referred to the Dakota. 

 Other strata are marine, but there is apparently a considerable differ- 

 ence between the Cretaceous of the mountain region and that of the 



plains. 



The Fort Union Beds. 



The Fort Union beds of the Fish Creek locality have been de- 

 scribed by the author in a former paper." As previously stated in 

 the present paper, I traced them over a quite large area from north- 

 east of Big Timber to the region north of Melville. 



The beds examined apparently comprise only a part of the series 

 and probably correspond in part to the dark shales and bands of sand- 

 stone which underlie the heavy massive sandstones at Bear Butte on 

 the Widdecombe Brothers' "Joe and Bill Ranch" near Fish Creek. 

 The sandstones contain impressions of plants, and there are occasional 

 thin beds of limestone containing fresh-water mollusca. The dark 

 shales weather into fine particles, which are sometimes flaky, and 

 they often contain bones of reptiles, Champsosaiirus, etc. Bones of 

 mammals are extremely rare. 



The question arises : What relations exist between the Bear Butte 

 beds, the so-called Fort Union near Glendive, the deposits of the 

 bad -lands of the Little Missouri, and the typical Fort Union beds near 

 the mouth of the Yellowstone River. The Bear Butte beds differ 

 somewhat in appearance from the deposits near Glendive, as they 

 contain more hard material (sandstones, etc.) yet there is much simi- 

 larity. Professor L. F. Ward made collections of fossil plants in the 

 Glendive beds, and he believed that collections from various localities 

 represented different horizons.'^ The Little Missouri beds are much 



'* " A Cretaceous and Lower Tertiary Section, etc.," Froc. Avier. Pliilos. Sor., 

 Vol. XLVI, No. 170. 



low Fioj-a of the Laramie Group," Sixth Annual Report of the U. S. Geological 

 Survey, p. 542. 



