WESTERN WYOMING AND BLACK HILLS 555 



Halysites catenulatus to Comstock in 1873,* for its features and relations 

 accord with the descriptions. A thickness of 150 feet was reported west 

 of Camp Brown. Professor Comstock, however, classified the formation 

 as Niagara on the old supposition that the Halysites was characteristic 

 of that age. Some observations as to the extent of this formation in the 

 Wind Eiver range and some other ranges west and northwest were made 

 by Professor St. John, of the Hay den survey, f In the Teton region the 

 same formation is described by this observer (page 480, Eleventh Keport) 

 as follows : 



"Niagara : Heavy bedded, buff, magnesian limestone, usually weathering in 

 castellated exposures 400 feet and less to 600 feet. In the southwest occurs 

 a local development of light colored, rough weathered quartzitic sandstone 50 

 feet or more in thickness, apparently occupying the place of the dolomite lime- 

 stone. Also local developments of drab shales, 100 feet more or less, occur in 

 this horizon." 



On the map of "Part of central Wyoming" in the atlas to the Twelfth 

 Hayden Eeport the formation is included in beds designated "Calciferous 

 series," which ends near the southeastern termination of the Wind Eiver 

 range at a point about 4 miles north of Sweetwater river. 



Ordovician in the Black Hills Uplift 



The Ordovician is represented in the Black Hills uplift by a formation 

 known as the Whitewood limestone. This has a thickness of 80 feet in 

 the vicinity of Deadwood, in the northern Black hills, but it thins rapidly 

 to the southward and disappears near Elk creek on the east side and at the 

 head of Eapid creek on the west side of the hills. The rock is hard, mass- 

 ive, somewhat silicious, and ordinarily of buff color with brownish spots 

 or mottlings. It contains large Endoceras, Maclureas, and corals of Tren- 

 ton age. It appears prominently in the Mgger Hill and Bear Lodge 

 uplifts, with a thickness averaging 60 feet. The manner in which the 

 formation thins out in the middle and southern portions of the Black 



Ulrich ; Trochonema umbilicatum, Hall; Hyolithus cf. baconi, Whitfield; Chiton cana- 

 densis, Billings ; Orthoceras near O. Olorns, Hall, and O. nicolletti, Clarke ; Actinoceras 

 cf. remotiseptum, Clarke (septa less distant). 



Mr Ulrich regards this fauna as of late Black River or early Trenton age, indicating 

 equivalency with the basal sandstone of the Bighorn formation in the Bighorn mountains 

 and with the Harding sandstone near Canyon City, Colorado. 



* Report upon the Reconnaissance of Northwestern Wyoming, made in the summer of 

 1873, by William A. Jones (War Department), 43d Congress, 1st Session, H. R., Ex. 

 Doc. 285, Washington, 1874, p. 112. 



t Twelfth Annual Report of the U. S. Geol. and Geog. Survey of the Territories for 

 1878, part 1, Washington, 1883, pp. 173-269, and Eleventh Report of the U. S. Geol. and 

 Geog. Survey of the Territories for 1877, Washington, 1879, pp. 325-508. 



