248 REPORT UNITED STATES GEOLOGICAL SURVEY. 
No. 43. Brownish-gray sandstone, thin layer. 
No. 44. Bluish arenaceous clays, with thin, indurated layers, 300 
feet, +. 
No. 45. Soft, bufi-gray sandstone, dip 15° N. 520 B., 30 feet, +. 
No. 46. a, veddish-drab and brownish clays; 0, lignite coal, 8 to 1 
inches, drab clay 12 inches, lignite 3 inches, drab clay 12 inches, lignit 
6 to 10 inches, total 4 feet ; 6, brown clays with selenite, 15 feet ; “total 
feet, +. 
No. 47. soft, light yellow sandstone, 20 feet, +. 
No. 48. a, soft, “erayish yellow, shaly sandstone and brown clays, ex- 
posed 10 feet; 6, drab-brown shales, with minute flakes of mica and sel- 
enite, 3 feet; C, brown, gritty shales, with selenite, 30 feet, + ; total, 60 
feet, ==. 
No. 49. Rusty brown and buff calcareous sandstone, 8 feet +, with nu- 
merous fossils In upper part, Inoceramus and several other conchifers, 
gasteropods, and Ammonites, probably identical with Fox Hills Creta- 
ceous forms. 
No. 50. Soft, yellowish sandstone and clays, imperfectly exposed, and 
belonging to a heavy bed at the top of the Mesozoic series here exposed. 
No. 51. Tertiary. Buff sandstones with more or less argillaceous mat- 
ter, resting unconformably upon the preceding sandstones, No. 50, in 
nearly horizontal strata. : 
No. 52. Yellowish clays, slightly brownish or reddish tinted above; 
possibly Pliocene or Post-Tertiary. 
No. 53. Morainal bowlder deposits crowning ridge 800 feet anare the 
level of Bull Lake. 
The few hours devoted to the examination at the above locality neces- 
sarily left the results less complete than could be desired. It is impos- 
sible to draw the line of demarkation between the Jurassic and Creta- 
ceous horizons, also between the former and the Trias. In the latter 
case, however, the great gypsum deposit affords a convenient horizon, 
but since this is evidently an excessive local development it might not 
subserve*even the purpose of convenience. A comparison of this part 
of the section with the equivalent horizon to the northwest exhibits a 
marked change in the lithology of the inter-Jura-Trias strata. We here 
lose entirely the well-developed yellowish or buff sandstone that occurs 
in this horizon at the confluence of North Fork and Wind River, although 
- the lower limestones correspond stratigraphically with occurrences at 
that locality, except for the paucity of organic remains in the present 
beds. It is hardly necessary to add that not the vestige of an organism 
was observed in the characteristically ‘red beds” of the Trias. The 
Jura, however, is recognized in the fossils occurring in the sandstones 
No. 25. But the limits of the formation above in the present state of 
knowledge must be arbitrarily assigned to some one of the lithologically 
conspicuous horizons interposed between No. 25 and No. 30. One or 
more of the sandstone and shale horizons occupying this space may prove 
to be identical with the Dakota or inferior formation of the Cretaceous. 
The heavy clayey measures No. 32-34, inclusive, doubtless represent the 
middle or Colorado group, while in the upper portion of the remainder 
of the conformable deposits, extending up to No. 50 and embracing a 
vertical thickness of strata probably in the neighborhood of 900 feet, a 
stratum occurs charged with a molluscan fauna ‘eminently characteristic 
of the Fox Hills division of the Cretaceous series. The lithology of 
these upper strata alone would strongly suggest the above inference. 
Although not a unique occurrence, the presence of lignitic deposits in 
these undoubted upper Cretaceous rocks at the present locality i is an in- 
