HISTORICAL SKETCH. Xill 
specimens of large orthocera, fragments of which measure a foot long and more than four inches wide. 
The faces of some of the rocks are covered with fuci, and in some producta form almost the body of the 
rock. These fossiliferous beds are separated from the great sandstone beds of the country, which here go 
far below the level of the river, by a thick stratum of eighteen feet of compact subcrystalline limestone 
without fossils. Below this stratum nothing but sandstone appears.” (Pp. 135-136.) He thus corrects 
Keating’s report (1823), in which it is said that a limestone formation underlies the sandstone at Fort 
Snelling. At St. Anthony falls ‘‘the immense slabs which have fallen from the limestone beds at the 
top are covered with producta, mixed with spirifers and cardia. * * * * * Toa geologist, however, 
it is exceedingly interesting, finding here the uninterrupted continuation, for one thousand miles, of the 
Carboniferous limestone, with its characteristic fossils.” (Pp. 136-137.) 
David Dale Owen. 
(lowa, Wisconsin and Illinois.) 
1839. Report of a geological exploration of part of Iowa, Wisconsin and Illinois, made 
under the direction of the Secretary of the Treasury of the United States, in the autumn of the year 
1889, by DAvID DaLE OwEn, M. D., principal agent to explore the mineral lands of the 
United States. 28th Congress, Ist Session, Senate document, 407, pp. 9-191, 1844. (Also 26th 
Congress, Ist Session, House of Representatives, document 239, pp. 9-161, 1845. The 
report was originally submitted for publication April 2nd, 1840, and was printed without 
the accompanying maps, charts, sections and other illustrations, June 4th, 1840. The fore- 
going editions were issued after the revision of the original, and the addition of some 
statistics and of all the accompanying illustrations. ) 
This report is confined almost exclusively to the lead region. The lead-bearing rock 
is embraced in the ‘Cliff limestone” which the author shows bears many points of similarity 
to the Carboniferous lead-bearing limestone of England. Notwithstanding this outward 
resemblance the organic remains require its assigament to a lower stratigraphic horizon. 
Tn the ‘‘Cliff limestone” Owen here includes a thickness of 500 feet of strata, extending 
from (and including) the Upper Silurian to the bottom of the Galena and Lower Silurian. 
He shows that this great member passes below the Coal Measures, instead of above them as 
thought by Keating, and is probably the equivalent of the Upper and perhaps of the Lower 
Silurian of Murchison, and of the Corniferous. Onondaga and Niagara limestones of New 
York, ‘‘and in part, perhaps, of the Champlain division.” The fossils of the underlying 
Blue limestone he considers closely like those of the Caradoc formation of England, and 
of the Trenton limestone and shales of the New York system. This is the first suggestion 
of the Trenton limestone in the valley of the upper Mississippi, but it should be datedfrom 
the publication of his revised report,—1844. 
“The most characteristic fossils of the cliff limestone of Iowa and Wisconsin are: (p. 25.) 
“Casts (often siliceous) of several species of terebratule. Some of them, probably, of new species. 
These are chiefly confined to the upper beds. ‘They are numerous and very perfect. 
“Several species of catentpora (chain coral) in greater abundance, and in more perfect preservation, than 
I have ever seen them elsewhere; among them the catenipora escharoides of Lamarck; the catenipora laby- 
rinthica of Goldfuss; and another species, not described by Goldfuss, nor elsewhere that I have seen—prob- 
ably new. I name it the catenipora verrucosa. * * * * These catenipora are very characteristic of the 
upper beds of the cliff limestone. They do not occur in the rich lead-bearing strata. 
‘SA coscinopora (the sulcata? of Goldfuss), the only coralline discovered in the middle and lower 
beds, and therefore characteristic of the true lead-bearing rocks. 
“Several species of calamopora, columnaria, tubipora, aulopora, sarcinula (costata?), astrea, cyatho- 
phylla, and caryophylla. These are found with the chain coral in the upper beds. 
