114 | GEOLOGY. 
pass into a pure white crystalline marble of great beauty, as at 
Cape Girardeau, and near Glencoe. 
Organic Remains. Fossils are abundant in all parts of the form- 
ation. Leptaena deltoidea, L. Sericea, L. Alternata, Orthis pecti- 
nella, O. testidudinaria, O. tricenaria, Rhynconnella capax, Murchi- 
sonia gracilis, M. bellicincta, Receptaculites sulcata, and Chaeteles 
Lycoperdon are mest common. 
BLACK RIVER AND BIRD’S—-EYE LIMESTONE. 
** They are bluish-gray or dove-colored, compact, brittle lime- 
stones, with a smooth conchoidal fracture. The beds vary in 
thickness from a few inches to several feet.’? ‘‘ Near the base, the 
rock is frequently traversed in all directions by vermicular cavities 
and cells.’’ : 
Gonioceras: anceps, Ormoceras tenuifolium, Cythere subleris are 
the most abundant fossils. 
IST MAGNESIAN LIMESTONE. 
This formation is developed in many parts of the State. It is 
usually a gray or buff, crystalline, cherty, silico-magnesian lime- 
stone, filled with small, irregular masses of a soft white or greenish 
yellow, silicious substance, which rapidly decomposes when exposed, 
and leaves the rock full of irregular cavities, and covered with 
rough, projecting points. These ragged, weather-worn strata, crop 
‘out in the prairies, and cap the picturesque bluffs of the Osage 
in Benton and the neighboring counties. 
These beds often pass into a homogeneous buff or gray crystalline 
magnesian limestone, which is frequently clouded with blue or 
pink, and would make a good fire-rock and building stone. At 
other places, the strata become compact, hard and clouded, as 
above, forming a beautiful and durable marble. 
Some of the upper beds are silicious, presenting a porous, semi- 
transparent, vitreous mass, in which are disseminated numerous 
small, globular, white, enameled oolitic particles. They are some- 
times in regular and continuous strata ; at others, in irregular mass, 
presenting mammillated and botryoidal,and drusy: forms of this 
EXPLANATIONS OF THE GEOLOGICAL MAP. 
The Quaternary System covers nearly the whole surface of the 
State, but it is represented by the light carmine color in the river 
bottoms only, where no other rocks appear on the Pertinacs All the 
ed. It 
face-clays, marls, and oaks? in all parts of the State belong to this 
syst The sands and clays of the Tertiary excepted. 
THE TERTIARY SYSTEM 
Is represented by the orange color, in Scott, Stoddard and Dunklin 
Counties, It is found only on the borders of the swamp country. 
THE CRETACEOUS (?) SYSTEM. 
These rocks are reprcsented by the drab shade on a small area 
in Scott County: 
COAL MEASURES 
Are represented by the purple. Many of the seeped are so small 
that they cannot be put down on a map of so smallas 
LOWER CARBONIFEROUS, 
Represented by the blue, skirts the edge of the coal measures 
from the Des Moines to southwest of the State, and down the 
Mississippi to Grand Tow 
beautiful mineral. In some parts of Benton and the neighboring 
Counties, these masses left by the denuded strata, literally cover the 
surface, and render the soil almost valueless for ordinary cultiva- 
tion. Other strata abound in concretions, or organic forms, which 
resemble wooden button-molds, with a central aperture and one 
convex surface. Masses of calcareous spar are quite abundant in 
the upper beds. But the lower part of this formation is made up 
of thin, regular strata, of a soft, earthy, light drab or cream-colored 
silico-argillaceous magnesian limestone, called cotton rock. 
Above the beds already described, we find, in several places in 
the State, a succession of hard, silicious, dark bluish-gray, semi- 
crystalline limestones, interstratified with grayish-drab, earthy, 
magnesian varieties, all in regular layers, destitute of chert. These 
strata have been joined to the rst. Magnesian limestone, with the 
expectation that they may prove distinct from the Calciferous sand- 
rock, and the rst Magnesian limestone, and be identified with the 
Chazy limestone, or some other formation. Straparollus laevata, 
asmall variety of Cythere sublevis, and a large Orthoceras, have 
been observed in these rocks. 
SACCHAROIDAL SANDSTONE. 
This formation is usually a bed of white friable sandstone 
slightly tinged with red and brown, which is made up of globular 
concretions and angular fragments of limpid quartz. It presents 
very imperfect strata, but somewhat more distinct lines of deposi- 
tion, variously inclined to the planes of stratification. 
This interesting formation has a wide range over the State. I 
have seen it in Ralls, Boone, Saline, Cooper, Moniteau, Pettis, 
Benton, Morgan, Hickory, St. Clair, Cedar, Polk and Dallas; and 
Drs. SHUMARD and Litron observed it in Perry, St. Francois, 
Franklin, Ste. Genevieve, and other Counties. 
Its thickness is very variable, from 1 to 125 feet. At times it 
thickens very rapidly, so much so as to increase thirty or forty feet 
in a few hundred yards. Ina bluff about two miles northwest of 
Warsaw, is a very striking illustration of this change of thickness. 
This sandstone crops out along the bluff, between the rst and 2d 
DEVONIAN SYSTEM, 
Represented by the dark green, covers a very narrow strip 
between the Carboniferous and Silurian rocks. It is often so thin 
and the area exposed so irregular that it is impossible to represent 
it on so small a map. his is particularly true in Ralls, Pike, 
Callaway, Hickory, Polk, Christian, and other Counties 
I have tried to place some. green in the region where these narrow 
and irregular areas are found. 
THE UPPER SILURIAN, 
Colored dark red, covers.only a small area in Cape Girardeau 
County. 
THE LOWER SILURIAN, 
Colored yellow, covers a large area in southeast Missouri. 
THE AZOIC SYSTEM, 
oo he India ink, has but a small area covered at - Pilot 
outcrops are so small it is impossible to represent 
og in pripniti on. 
THE IGNEOUS ROCKS, 
Colored with the bright carmine, are developed in numer 
r areas, many of them much too small to be i ata 
ot 
