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fill and the culverts. This disturbed site contains a 
mixture of native forest and prairie species, as well 
as some common weeds of European origin. 
The chief objects of interest in this locality are 
the cave, fig. 14, and springs. Bretz & Harris (1961) 
described the cave as follows. ‘‘Entrance to this 
cave is through a roof breakdown. A network of joint- 
controlled vertical slots that should not be negotiated 
without a rope is immediately encountered. Two sets 
of joints cross at approximately right angles. Ceilings 
Fig. 14.-- Entrance to Twin Culvert Cave. Because of 
the nature of this cave, ropes, ladders, and ample light 
should be available if its exploration is attempted. 
and depths appear to vary along each set.’’ The cave 
is sometimes visited by a large colony of gray bats, 
Myotis grisescens, a migratory species that is poorly 
known and is rare in collections. 
Twin Culvert Cave is presently in private owner- 
ship. 
9. COLE CREEK HILL PRAIRIE 
Cole Creek hill prairie is located in the north- 
west quarter of section 4, T. 9 N., R. 13 W., 2 miles 
south of Eldred, Greene County. The prairie occupies 
part of a bluff of the Illinois River and part of the 
north bluffs of Cole Creek. This locality was previ- 
ously described under the name South Eldred hill 
prairie (Evers 1955). 
The bluft of the Illinois River has a small toe 
slope, a limestone cliff, and a loess-covered brow 
slope. The bluffs of Cole Creek also have a loess 
cover but no visible rock outcrops. The loess was 
deposited during Wisconsinan time. 
Vegetation characteristic of hill prairies covers 
about 4.5 acres of two southwest-facing slopes that 
form an inverted U, the prongs of the U extending 
downslope, fig. 15. Little bluestem is the dominant 
grass. Some other grasses of these slopes are big 
bluestem, Indian grass, side-oats grama, and Scribner’s 
panic grass. The bluets Houstonia nigricans grows in 
this prairie, which is near the northern limit of the 
range of the species in Illinois. On October 1, 1958, 
Fig. 15.-- One of the spurs of the hill prairie along 
Cole Creek, south of Eldred, Greene County. Forest with 
many chinquapin oaks grows in the coves. 
29 stems of nodding ladies’-tresses, fig. 16, were 
observed in this prairie. 
The toe slope, the ravine between the prongs of 
the U, and the bluff-tops support a deciduous forest 
in which common tree species are white ash, Ameri- 
Fig. 16.—- Nodding ladies’-tress. In 1958, 29 stems of 
this species were observed in Cole Creek hill prairie. 
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