6T.J0HN.] CARIBOU RANGE. 363 



bedding, associated with red shales, which stand in various positions, or 

 dipping from vertical at one point 05°, IS". 45° E., changing in a short 

 distance to the opi)osite direction at a steeper inclination. This con- 

 tinues to be the character of the ridge to its northwest extremitj', A\hero 

 it is broken down in a low saddle at the h-ead of Mosquito Gulch, which 

 connects it with tlio highlands to the northwest on v,'hich Station XIX 

 was located, about three miles distant from Station XVIII. At the lat- 

 ter point the ridge shows an interesting section. The last-mentioned 

 sandstone horizon, forming a brown M'eathered ledge with red shales, 

 outcrops in the south declivity a hundred yards from the summit, and 

 dips steeply southward. A little higher in the slope, a heavy ledge of 

 (12) bhiish-drab, spar-seamed limestone forms a break in the steep de- 

 scent, the dip ranging from 45° to 60°, S. 30° to 40° W. It contains 

 numbers of a small (lastreopod and very imperfect Lamellibranchiates, 

 and vertebrate remains. Of the latter, only a few indeterminable frag- 

 ments of bone, and a single specimen of a vertebra, rewarded a carefid 

 search. The Gasteropods are undistinguishable fi'om a form occurring 

 elsewhere in i)ost-Jurassic de])osits, and the Lamellibranch may prove 

 to belong to the genus Unio. Professor Cope's determination of the croc- 

 odihan affinities of the vertebra also bears strong, though not conclusive, 

 evidence in favor of the transitional or early Ccuozoic age of these de- 

 posits. The limestone is immediately succeeded by ( 13) indurated broAvn- 

 ish ferruginous deposits, also containing obscure Ibssils, apparently a 

 Lamellibranehiate shell. The crest of the ridge immediatelj' above the 

 latter exposure is formed by a heavy bed of (14) hard, grayish blue, 

 rusty weathered, spar-seamed, brecciated sandstone, with slickeuside 

 surfaces, and much broken up. It dips 75°, S. 30° W., in places verti- 

 cal. 



From the foregoing observations it is apparent that we at the outset 

 of oiu' examinations along the outlying southwestern border of the range 

 encounter evidences of the extraordinary character of the disturbances 

 which constitute so prominent a feature in its dynamical geology. In 

 the short sj^ace gone over there are two sharj:) folds, that on the crest of 

 which Station XVIII is located, pitching steeply to the northeastward, 

 and in places thrown beyond the vertical, reversing the order of suiier- 

 position of the strata involved in the overturn. The northeast face of 

 Station XVIII ridge falls rapidly into the gulch of the main northwest 

 branch of the East Fork, over a decli^dty covered with dense thickets 

 and coniferous forests. Beyond lies a far more broken and higher mount- 

 ain region, cidminating in Station XXV, 10 miles to the northeast, which 

 overlooks the lower valley of the Snake between Pyramid and Fall 

 Creeks. To the north, this ridge attaches to the water-shed at Station 

 XIX, northwest of which it sinks into a broad depression some six miles 

 across and 800 feet in depth, opening a low pass from Willow Creek, via 

 FaU Creek, across to the lower valley of the Snake. This pass is very 

 like the depression at the head of McCoy Creek, though the cafioned 

 course of Fall Creek affords a less practicable route for a highway than 

 the more open valley of the former stream. The view looking south and 

 southeast embraces the basin ridges west of Gray's Lake, and the crater- 

 like northwestern face of Mount Caribou, and far in the distance, in the 

 direction of the Wind Eiver Mountains, a line of snowy peaks stretches 

 across the horizon. 



Approaching Station XIX from the vaUey of Willow Creek, a section 

 is crossed which extends oiu" knowledge of the comjionent strata in a 

 belt still more northerly than that just noticed. The way leads hi a gen- 

 eral northerly course a distance of about sis miles, the southern third or 



