222 REPORT UNITED STATES GEOLOGICAL SURVEY. 
only obscure exposure; dip H. 8° N., at an angle of 50°. At one point 
the sandstones, which are in places calcareous, afforded a few imperfectly- 
preserved fossils, amongst which Dr. White has determined the follow- 
ing Cretaceous forms: Mactra arenaria Meek?, Ostrea sp.?, Inoceramus 
erectus Meek?, and other undetermined conchifers. The I nocerami have 
a considerable vertical range in the heavy sandstone deposit, although 
its presence is chiefly determined from mere fragments showing the pecu- 
liar shell structure. 
No. 12. The steep hills in the immediate vicinity of the main forks of 
the stream are made tp cf gray, buff-weathered sandstones and drab 
clays, inclined at an angle of 55° H. 33° N. 
No fossils were observ ed in the latter beds of the above section, but 
there is no doubt of their conformable superposition to the strata de- 
scribed under No. 11, and which, together with No. 4-11, inclusive, 
constitute a heavy series of light gray and yellowish- weathered sand. 
stones and drab clays occurring “within the basin area proper, and whose 
disturbed condition is apparently attributable to, and synchronous with, 
the disturbances that folded the strata over the region of what is now 
the Gros Ventre Range. 
Station X XIX was located on a commanding crest of the ridge just 
west of the main branch of the Gros Ventre, about 6 miles southeast of 
the forks. The view from this point commanded nearly the whole 
northeastern front of the Gros Ventre Range, besides nearly the entire 
extent of the basin from a nearly central position. The nature of the 
strata composing the ridge itself, in the main soft sandstones and clays, 
dipping northeastward, affords few rock exposures of any considerable 
vertical extent. But the surface of the whole region, reaching up to and 
crowning the sharp ridge on which the topographical station was made, 
is strewn with the remnants of a remarkable conglomeritic deposit, 
whose origin might at first be mistaken for Quaternary, as indeed the 
degradation and dispersion of its component materials was affected 
during that period. Approaching the valley of the Gros Ventre, the 
Cretaceous deposits have been extensively eroded, but to the southeast 
they rise up into higher ridges, which still farther in that direction have 
been denuded, bringing to view the Triassic ‘‘red beds” and drab vari- 
egated deposits of the Jura in the before-mentioned low arch to the 
northeast of Gros Ventre Peak. This arch is about southeast of Station 
XXIX, to the east of which the Cretaceous deposits, if they still exist 
in that quarter, merge into the undulating drainage divide defining the 
southern limits of the basin. 
In this connection may be mentioned limited occurrences, in the direct 
line of the south-southeasterly strike of the deposits above noticed, that 
were examined along Green River just above the great bend. There 
here occurs an exposure of gray and bluish clays with bluish indurated 
fine arenaceous layers, which break into narrow slabs or post-like masses, 
the dip of the beds being about N. 40° E., at an angle of 30°. The 
isolation of the exposures and the absence of fossils renders the deter- 
mination of their stratigraphical position a difficult question. But there 
is certainly a somewhat striking coincidence in the direction of their 
strike, which, at least, suggests a possible identity with the above-men- 
tioned deposits in Station X XIX ridge. 
The general northwesterly strike of the Cretaceous deposits, in the 
Gros Ventre section above described, apparently veers round more to 
the west on passing into the region nor th of this stream. This is indi- 
cated by the occurrence of very similar lithelegical manifestations iz 
the umole slopes inidway between Mount Leidy and the Gros Ventre, 
