90 Review of Owen's Geological Report on Wisconsin, Towa, ete. 
Many of the fossiliferous beds of this formation are densely crowded 
with organic relics; as much so as the most fossiliferous of the blue 
limestones of Ohio, Indiana, and Kentucky. The proportion of genera 
and species, it is true, is not great, but the number of individuals is im- 
mense ; some slabs are so covered with shells, that it would be difficult 
to place the finger on a spot without touching some of them 
If we except the white sandstone, the uppermost bed of P.1 e, that 
upon which the Lower Magnesian Limestone (F. 2) rests, nothing de- 
finite was known, up to the thee of the present survey, of the nature 
paleontological evidence as to the exact place which these strata oceu- 
ied in estern geological series. It is, therefore, with no small 
delves of satisfaction that I find myself able to disclose a new feature 
in the paleontology of Western America, and thus to furnish, not only 
to the geologist a key to the stratigraphical position of the rocks north 
of the Wisconsin River, but, at the same time, to the miner his surest 
and safest ie by which to direct operat ons in mee search her mineral 
wealth.”— 
The immense extent of the protozoic rocks chiefly belonging 
to its lower division seems to be a remarkable feature of the geol- 
ogy of the Northwest. The area of the “Lowest Sandstone” 
where it is fairly ce cannot be less than 12,000 square miles; 
and that concealed by drift at least as much more, within the 
confines of the United states. "These sandstones attain a thick- 
ness in the best exposed sections on the Mississippi and Wiscon- 
sin rivers of upwards of 500 feet. he calcareous beds of the 
me period are fully as extensive. Commencing on the Missis- 
sist in Jat. 41° 30’, they prevail to the Wisconsin and Turkey 
rivers, and thence capping the above-mentioned sandstones, they 
stretch, with little interruption, on both sides of the Mississippi, 
to within a few miles of the Falls of St. Anthony ; thence up 
the valley of the Minnesota river, nearly to its confluence with 
the Lesueur river; and after being lost under the drift, they reap- 
pear at the Great South Bend of tein river of the North, at Lower 
Fort Garry and Great Lake Winnepeg. 
he upper pase Sr — has, in the valley of the Mis- 
sissippi River, sout isconsin and Turkey rivers, a length 
from north to south “of nearly 100 miles, and even a greater 
width from east to west, giving an area of at least 11,000 
square hil North of Wisconsin and Turkey rivers to the 
St. Croix valley, the lower magnesian limestone has a length 
from northeast to southwest of 160 miles, with an average width 
of nearly 50 miles, giving an area of 8000 miles, and this without 
its extension in the valley of Red River = the — ~~ under 
* See Tab. 1, B. Fig. ¥ 
