WORK OF EARLY INVESTIGATORS 379 



coarse, sandy intercalations; sixthly, a reddish yellow sandstone, which is imme- 

 diately succeeded by a brick red, compact sandstone of the Trias. In the marls, 

 both above and below the limestones, which lie a little above the middle of the 

 series, occur numerous Jurassic forms, anions them the following : 



"Pentacrinus asteriscus, Belemnites. densus, Tancredia warreniand, and Trigonia quad- 

 rangular is." 



Since the days of Hayden and the Fortieth Parallel Survey nothing 

 of geological importance has been published relative to this portion of 

 Wyoming, which is a peculiar combination of plains, tablelands, valleys, 

 canyons, hills, and mountains. Unfortunately, a complete description 

 of the topographical features must be deferred to some future time, and 

 only those referred to that are directly associated with the Jurassic ex- 

 posures. 



Mountain Ranges, Folds, and Faults 



The Laramie mountains, the longest range, extend from the Colorado 

 line north to Laramie peak, and thence north and westward to the North 

 Platte river. Westward from the Laramie mountains, across the Laramie 

 plains, are the Medicine Bow mountains, which are the northern exten- 

 sion of the Park range, nearly paralleling the Laramie mountains, and 

 are found as far north as Elk mountain, where the older rocks disappear 

 beneath the more recent. In the western-central part are the Shirley 

 mountains, which are in reality the Seminoe mountains, on the east side 

 of the North Platte river, and north of these the Indian Grove moun- 

 tains, which are granite peaks scattered along the east side of the 

 North Platte river, as far north as the Sweetwater river. Beside these 

 prominent elevations are the Freezeout hills east of the Shirley moun- 

 tains and the Hartville hills north of Fort Laramie. There are also 

 several anticlinal folds and some faults that have played an important 

 part in exposing Jurassic bands. South and east of the Freezeout hills 

 are four anticlinal folds extending northeast and southwest or at a right 

 angle to the Freezeout uplift and other orographic movements about the 

 Laramie plains. Singularly enough the forces making these folds oper- 

 ated from the southeast, while those making the mountain ranges came 

 from the west and south. These folds are only a few miles apart and 

 vary from 8 to 20 miles in length. The} 7 may hereafter be known by the 

 following names, commencing at the one nearest the Freezeout hills : 

 Medicine,* Como,t Prager,J and Mis.er.§ Southwest of Laramie 20 miles 



* Named from the Medicine Bow river, which is in this vicinity. 

 fThis has been referred to many times as the Como uplift. 



1 Named in honor of Frank Prager, the oldest pioneer in this region. 



2 Named from Miser siding, which is located on this fold. 



