144 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



The coal field of Missouri and Iowa covers about 35,000 square miles. 

 This western field is very shallow, consisting of three well marked di- 

 visions — (1) an upper siliceous, 100 feet; (2) middle argillaceous, 75 feet; 

 (3) lower calcareous, 100 feet. The middle division carries the coal, 

 the coal layers having a thickness of four or five feet. 



Passing from the mouth of Iowa River to that of the Des Moines, the 

 " Subcarboniferous limestone " occurs "with no coal seams." There the 

 Mississippi passes through a corner of the Illinois coal field. The lime- 

 stone thins out here and the Coal Measures rest on u the limestones ot 

 Devonian age." At the junction of the Missouri and Mississippi, " Car- 

 boniferous limestone" is found which just underlies the lowest work- 

 able seam of the Illinois field. 



In the same year, in association with B. F. Shumard, Owen published 

 some statistics regarding the fossils obtained during the survey. 1 



The authors found in the Devonian rocks of these States 49 species, 

 included in 26 genera, and in the Carboniferous 120 species, included in 

 49 genera. 



" Of the above genera 5 are peculiar to the Devonian and 3G to the 

 Carboniferous." • * * " Eight genera are common to the Silurian 

 and Devonian, 10 to the Silurian and Carboniferous, 10 to the Devonian 

 and Carboniferous, and 9 are common to the three systems." 



Two- thirds of the 39 species from the Devonian rocks between Park- 

 hurst and New Buffalo, on the Upper Mississippi, are identical with 

 those found in the coralline beds of the falls of the Ohio at Louisville 

 and Charleston Landing, Indiana. u Thirteen species are identical 

 with European forms." 



Twenty -four of the 120 Carboniferous species found mainly in Iowa, 

 are identical with European species. While over one-half of the Bra- 

 chiopoda are identical with (" can be referred to ") European species, 

 only two out of 52 Crinoids are common to the two countries. 



Polyparia are most abundant in the Devonian, while Acephala are 

 most numerous in Carboniferous rocks. 



Mr. H. King, 2 in 1851, published a paper in which he commented upon 

 a section running from St. Louis southwest to Iron Mountain and Pilot 

 Knob. He observed that above the so-called " Mountain limestone " or 

 " Yoredale limestone," upon which St. Louis stands, occurs a coal bed 

 having au average thickness of 4 feet. This coal deposit is not an out- 

 liner of the Illinois coal basin, but a continuation of it. Passing over 

 the southern point of this basin, we meet again the u Mountain lime- 

 stone " which the author for convenience named " St. Louis limestone j " 

 he considered it, both from its position and fossils, as strictly Carbon- 

 iferous. Its thickness was estimated to be between 500 and 600 feet. 



'Oweu.D. D., and B. F. Shumard : On the number and distribution of fossil species in the Paleo- 

 zoic rocks of Iowa, Wisconsin, and Minnesota. Am. Assoc. Proc, vol. 5, 1851, pp. 235-239. 



2 King, H. : Some remarks on the geology of the State of Missouri. Am. Assoc, Proc, vol. 5, 1851 % 

 pp. 182-199. 



