PAPERS ON GEOLOGY 261 
THE THEBES SANDSTONE AND ORCHARD CREEK 
SHALE AND THEIR FAUNAS IN ILLINOIS 
T. E. SavaceE, UNIVERSITY OF ILLINOIS 
The Thebes sandstone was named by Worthen’ in 1866 from 
the town of Thebes, in Alexander County, Illinois, near which 
the formation is well exposed. This sandstone is known in 
Illinois over only a relatively narrow area bordering Missis- 
sippi River in the southwest part of the State. West of this 
the strata extend into adjacent portions of Missouri, and out- 
crop in several places in the vicinity of Cape Girardeau. The 
total thickness of the formation in this region is about 75 feet. 
The basal portion of the Thebes sandstone is exposed along 
a small stream in the south part of the town of Thebes, where 
it rests unconformably upon the Fernvale (early Richmond) 
limestone. This lower sandstone is here fine grained, yellow- 
ish brown, and micaceous, with a thickness of 6 or 8 feet, 
and grades upward into a coarser grained, bluish sandstone 
with few fossils. 
The following species of fossils are common in the fine 
grained basal phase of the Thebes sandstone: 
Climacograptus putillus Hall. 
Lingula ovoides n. sp. 
Conularia ornata n. sp. 
Isotelus brevicaudatus n sp. 
Endymionia bellatula, n. sp. 
The lower horizon of the Thebes sandstones containing En- 
dymionia bellatula is exposed again farther north in the south 
bank of Madison Creek, in the S. E. quarter section &, T. 11, 
S. R. 2 W., in Calhoun County. The sandstone here is 
yellow to buff, and thin bedded. It rests unconformably 
upon the Kimmswick limestone, and passes upward into a bed 
of sandy shale. 
Still farther north, in Pike county, Missouri, a sandstone 
that corresponds to the basal portion of the Thebes formation 
is exposed along a stream one-half mile west of Dover Church. 
1. Worthen, A. H., Geol. Survey of Ilinois, Vol. I, p. 139, 1866. 
