IOWA CAMBRIC SUCCESSION 
315 
correlations in the north. Thus, the Julian (Galena), or lead¬ 
bearing, dolomite was called by Schoolcraft,® in 1823, the Metal¬ 
liferous Limestone, and was referred to what was later termed 
the Carboniferous section in England. In the same year the same 
formation was termed by Keating® the Magnesian Limestone, and 
regarded as the equivalent of the Permian Magnesian formation 
of northern England. By Featherstonhaugh^ in 1835, it was 
designated the Galeniferous Limestone—another Carbonic name. 
In 1840, Owen® thought all the strata beneath the Peter sand¬ 
stone of the lead region were Devonic in age; but he quickly 
changed^ this part of the section to Murchison’s Lower Silurian. 
This last mentioned term continued to be used exclusively in this 
country until about 1872, when Dr. T. Sterry Hunt^® advocated 
the adoption of Sedgwick’s title Cambrian. In this he was fol¬ 
lowed by Prof. James D. Dana.^^ However, Dr. Gerard 
Troost^^ 30 years before, was probably really the first person to 
use properly the Sedgwickian name in America. 
The Paleozoic strata below the Peter sandstone are conspicu¬ 
ously grouped into an upper, dominantly dolomitic sequence, and 
a lower, distinctly arenaceous succession. This distinction is 
early reflected in Owen’s titles Lower Magnesian Formation and 
Lower Sandstone. In late years these terms are slightly modified 
into Magnesian series and Siliceous series. The United States 
Geological Survey further endeavors to fix Owen’s subdivisions, 
ex cathedra, by proposing for the upper member a new geographic 
name, designating the dolomites the Prairie du Chien formation. 
It is not quite clear at this distant day just how much of a 
section Owen originally intended to include in his Lower Mag¬ 
nesian terrane. Although he apparently embraces all of the dolo¬ 
mitic beds so high as the Peter sandstone, it is doubtful whether 
5 Narrative Journal of Travel, etc., to Source of Mississippi River, Cass Exped., 
414 pp., Albany, 1821. 
6 Narrative of Exped. to Source of St. Peter’s River, etc. under Maj. Stephen H 
Long, two vols., Philadelphia, 1824. 
7 Rept. Geol. Rec. to Coteau du Prairie, p. 158, Washington, 1836. 
8 Rept. Geol. Expl. Iowa, Wisconsin and Illinois, 26th Cong., 1st. Sess., House 
Doc. No. 239, 161 pp., 1840. 
9 Twenty-eighth Cong., 1st Sess., Sen. Doc. No. 407, p. 32, 1844. 
10 Canadian Naturalist, N. S., Vol. VI, p. 281, 1872. 
11 Am. Jour. Sci., (3), Vol. VIII, p. 218, 1874. 
12 Tennessee Geol. Surv., Sixth Ann. Rept., p. 4, 1841. 
