F. B. Meek and A. H. Worthen on the Age, etc. 167 
The relative proportion of the several species may perhaps 
be set down as follows: 
Populus monilifera. 
cus macrocarpa. 
Quercus alba and Quercus rubra. 
Tita Americana, Ulmus fulva and Quercus discolor. 
Juglans nigra, Ulmus Americana. 
Carya alba, Carya glabra. 
Fraxinus Americana, Celtis occidentalis. 
Juniperus Virginiana, Platanus occidentalis, 
. Acer rubrum, Gymnocladus Canadensis. 
Besides the above mentioned, of the smaller varieties there are 
Tunus Americana, Zanthoxzylum Americanum, Staphylea trifo- 
lia, Negundo aceroides, Corylus Americana, Carpinus Americana, 
Alnus incana, Euonymus Americana, Cercis Canadensis, us 
sericea, ? 
In the Omaha land district, which contains something like 
4000 square miles of land, there appears from the plots in the 
office to be about 75,000 acres of timber. A tract of country of 
equal size lying west of it would contain much less. 
The botanical names above corrrespond to and have been 
compared with the descriptions in Gray’s “ Manual.” 
Omaha, Nebraska, April 2, 1861. 
we SS St i So be 
4 
Arr. XVIII.—Remarks on the Age of the Goniatite Limestone at 
Rockford Indiana, and its relations to the “ Black Slate” of the 
Western States, and to some of the succeeding rocks above the latter ; 
by F. B. Meek and A. H. Worruen, of the Illinois State 
Geological Survey. 
Iv is known to most of those who have studied a sito 
illaceous limestone, and contains, in additi 
ae which it takes its name, other fossils ar esc to Spogive, 
No other rock is seen above or below this at ig iete ce 
locality, but in sinking wells in that vicinity it nae ee ascer- 
tained that it rests upon a Black Slate forming a mar orizon 
