E. S. Lull — Mammals and Horned Dinosaurs. 329 



division, lies in the present Niobrara County, hence the inap- 

 propriateness of the older formation name. 



Niobrara County is crossed from east to west by an important 

 watershed, Pine Ridge, which continues eastward into Sioux 

 County, Nebraska. South of this ridge, the land, with an 

 average elevation of about 5000 feet, is drained by the Niobrara, 

 although two small tributaries of the Platte rise in the south- 

 western portion. North of Pine Ridge the land falls abruptly 

 for about a thousand feet, and is drained hy the Cheyenne or 

 its tributaries. Of the latter, Lance and Lightning creeks, 

 together with Buck and Sage creeks, are the most important, 

 the first mentioned giving its name to the formation. The 

 map presented herewith (figs. 1 and 2) has been compiled 

 largely from the General Land Office map of the state of 

 Wyoming bearing the date of 1892, with such additions as 

 Hatcher's field maps, thrice published (1896, 1907) seem to 

 imply. This map has been submitted to Mr. Peterson for 

 revision as to localities, but is only tentative and merely serves 

 as a means of recording such otherwise perishable information 

 as we now possess. It will show quite clearly the general 

 relation of the Lance beds to the drainage, but the indicated 

 boundaries of the formation, although based upon Hatcher's 

 map, are only approximate, as the line of demarcation between 

 the Fox Hills and Lance on the one hand and the Lance and 

 Fort Union on the other is not clearly defined. As one ap- 

 proaches the locality from the east from Sage Creek, he 

 climbs a gentle declivity for a distance of about 2 miles until 

 near the summit of the divide separating the valley of Sage 

 Creek from that of the parallel-flowing Buck Creek. Here the 

 first escarpments are seen, of yellow sandstone, capped by hard 

 brown concretionary masses and containing marine Cretaceous 

 shells. From this divide several smaller canyons run with a 

 general western trend to the bed of Buck Creek itself. These 

 canyons are divided by pine-clad hills, with cottonwoods here 

 and there along the water courses. In one such canyon near 

 a strongly alkaline spring we pitched our camp. 



From Buck Creek the land rises rapidly toward the west and 

 north until the summit of the divide separating the watershed 

 from that of Lance Creek is reached, when the land again 

 descends to the latter stream. This area is grassed over, cot- 

 ton*wood trees following the main courses so that the latter are 

 thus clearly indicated. Here and there are fairly deep tribu- 

 tary canyons where the ever-varying stratigraphy may be traced. 

 The beds are alternating shales and sandstones with occasional 

 bands of lignite. The sandstones in the canyons were mostly 

 fairly hard, yellowish to whitish, often much cross-bedded and 

 capped with a much harder brown sandstone, which often had 

 the appearance of concretions. Some of the "concretions" 



