‘Review of Owen’s Geological Report on Wisconsin, Iowa, etc. 89 
_ Without assuming to determine the much-disputed question of an 
absolute palwozoic base, it may be safely asserted that the fossiliferous 
strata above referred to, exhibit the true base of the zoological series in 
the arg Valley. 
It was in August of 1847, while descending the St. Croix, that I first 
Pe meats m8 of Lingulas and ” wee disseminated in srata 
abutting against the protruding trap r which eross the stream at 
its falls. In tracing out the panlnals pve of these strata, during 
as in the above instance, in almost immediate contact with the trap or 
granite, or else separated from these only by the lowest member of F. 1 
Their depth below the base of the to yer Magnesian Limestone, I 
found to be not less than five hundred fe 
I observed, cet that besides icra: sa Orbiculas, there occurred 
in the sandstones of this formation, (above the Lingula grit, however) 
other Bendbionmih and sckoral forms of Crinoidea, found in peculiar 
green dolomitic interpolations.* 
In October of the same year, while measuring sections on the Missis- 
sippi, between the Falls of St. Anthony and the mouth of the Wiscon- 
sin, I discovered within a few feet of low-water mark, ten miles see 
Mountain Island, on the west side of the Mississippi, laminated grits a 
siliceo- calcareous layers, charged with an Obolus, neebatts cone 
remarkable on account of the spines with which it is provided, project- 
ing backwards from the margin of the pygidium. 
Convinced that the formations of Iowa and Wisconsin were destined 
to divulge new facts relative to the re base in Western America, 
I caused to be instituted, during subsequent surveys in 1848, 1849, and 
1850, 
favorable locality. The result showed, beneath the Lower Magnesian 
Limestone, at least six eer Trilobite beds, separated by from: 10 to 
150 feet of intervening strat 
I communicated this fact, in general terms, in my Preliminary Re- 
port of October 11, 1847, and mo - at large in my Annual Report for 
1848, Peer in the spring of 1 
est species of Tolobite obiained in this formation, and which 
k 
afew feet above the water level on Lake St. Croix, imbedded in a 
species of hydraulic limestone _ fifth Trilobite bell, near the top of 
member d, of F. 1. 
itis ofa coarse, bff, crystalline varaty of these bed as follows: 
Thoolatle earthy 5 matter, a, ; E $4 
Carbonate o i 48°24 
Carbonate o pase P 4243. 
gpa Py ne with a trace ee alumina, rage 614 
Sxoomp Sunizs, Vol: XVI, No. 46.—Joly, 1053. °° 8 
