OF ARKANSAS. 115 
C3 
sponges; but less sym- 
metrical, and without 
any apparent porous 
structure. They are, 
most likely of vegetable 
origin, and may, per- 
haps, be referrible to that 
obscure order of marine 
plants, known under the 
name of fucoides; but, 
| if so, are entirely differ- 
Shales, including an inch or two of coal, in ent tn form ‘om ie 
the cant below Cato’s spring. : thing of the kind I have 
ever observed before, or 
seen described in any of 
the works on fossil bo- 
Inches. 
7 
Fire clay and shale. 
o 
o 
fy 
— i 
J 
[s|s| 62 Sandstone. 
u |} 4? Pentrimital limestone. 
ee tany. 
jm |e In the collection of 
| t [| 304 | Archimedes limestone. ‘| W. Washburn, I saw 
At . some fine specimens of 
lepidodendrons, which 
have weathered out of 
= epee some of the higher sand- 
EL, Caleareous band, with pyrites ? stones of the preceding 
Gypsiferous shale. section; and imperfect 
specimens of the same 
fossil plant were observ- 
ed by members of the geological corps in the adjacent sandstone ridges. 
This is a plant which occurs in the millstone grit, but more abundantly 
at the base of the coal measures. 
It is a question of interest and importance, to determine whether any 
portion of the upper sandstones and shales of Washington county can be 
referred to the true coal measures; since, in that case, there would be 
hope of finding thicker and more valuable beds of coal in this county than 
have yet been discovered. Atpresent no coal beds are known of more than 
18 or 20 inches; except one, with a clay parting, in Mountain township, 
on the head of the Illinois river, 6 or 7 miles east of Boonsboro, which is 
about two feet thick; and those beds, at present known, in the immediate 
vicinity of Fayetteville, in shales under the millstone grit, do not exceed 
one foot. 
Black shale with carbonate of iron. 
