410 CARBOISriFEROUS LIMESTONE OF N. AMERICA. [Cii. XXV 



boniferous." The prevailing shell wliicli characterizes the carbonaceous 

 schists of this series, both on the Continent and in England, is Posido- 

 nomya Becheri (fig. 535). Some well- 

 known mountain-limestone species, such "' 

 as Ooniatites crenistria (see fig. 530) 

 and G. reticulatus, also occur in the 

 Hartz. In the associated sandstones of 

 the same region, fossil plants, such as 

 Lepidodendron und the allied genus 

 Saginaria^ are common; also Knorria, 

 Calamites Suckovii, and C. transi- ^''ToTeTcZZ'ntferL^''^^ 

 tionls, Gopp., some peculiar, others spe- 



cificall}^ identical with ordinary coal-measure fossils. The true geological 

 position of these rocks in the Hartz was first determined by MM. Murchi- 

 son and Seds'wick in 1840.^ 



CARBONIFEROUS LIMESTONE IN NORTH AMERICA. 



The coal-measures of Nova Scotia have been described (p. 3*77). The 

 lower division contains, besides large stratified masses of gypsum, some 

 bands of marine limestone almost entirely made up of encrinites, and, in 

 some places, containing shells of genera common to the mountain lime- 

 stone of Europe. 



In the United States the carboniferous limestone underlies the pro- 

 ductive coal-measures ; and, although very inconspicuous on the margin 

 of the Alleghany or Great Appalachian coal-field in Pennsylvania, it ex- 

 pands in Virginia and Tennessee. Its still greater extent and importance 

 in the Western or Mississippi coal-fields, in Kentucky, Indiana, Iowa, 

 Missouri, and other western states, has been well shown by Dr. D. D. 

 Owen. In those regionsf it is about 400 feet thick, and abounds, as in 

 Europe, in shells of the genera Productus and Sinrifer, with Pentremites 

 and other crinoids and corals. Among the latter, Lithostrotion hasalti- 

 forme or striahim (fig. 516, p. 404), or a closely-allied species, is common. 



* Trans. Geol. Soe. London, 2d series, vol. yi. p. 228. 

 I Owen's Geol. Survey ofWisconsin, <fec., 185?.. 



