522 



MOUNTAIN LIMESTONE. 



[Ch. XXV. 



Fig. 5S3. 



be restricted to a very few species, among which Textularia, Nodo- 

 saria, Undothyra, and Fusulina (fig. 583), have "been 

 recognized. The first two genera are common to 

 this and all the after periods ; the third has been 

 found in the Upper Silurian, but is not known above 

 Fumiina cyiin- the Carboniferous strata ; the fourth (fig. 583) is 

 drica, D'Orb. peculiar to the Mountain Limestone, and is charac- 



Magnified 3 diain. ^^ q£ ^ formation in the United g tates Arctic 

 Mountain Lime- . . . 



stone. America, Russia, and Asia Minor. 



STRATA CONTEMPORANEOUS WITH THE MOUNTAIN LIMESTONE. 



Fig. 5S4. 



In countries where limestone does not form the principal part of 

 the Lower Carboniferous series, this formation assumes a very differ- 

 ent character, as in the Rhenish Provinces of Prussia, and in the 

 Hartz. The slates and sandstones called Kiesel-schiefer and Younger 

 Greywacke (Jungere Grauwaeke) by the Germans, were formerly re- 

 ferred to the Devonian group, but are now ascertained to belong to 

 the " Lower Carboniferous." The prevailing shell which character- 

 izes the carbonaceous schists of this series, both on the Continent and 



in England, is Posidonomya Becherl 

 (fig. 584). Some well-known moun- 

 tain-limestone species, such as Go- 

 niatites crenistria (see fig. 579), and 

 G. reticulatus, also occur in the 

 Hartz. In the associated sandstones 

 of the same region, fossil plants, such 

 as Lepidodendron and the allied ge- 

 nus Sagenaria, are common ; also 

 Knorria, Calamites SucJcovii, and 

 C. transitionis, Gopp., some peculiar, 

 others specifically identical with ordinary coal-measure fossils. The 

 true geological position of these rocks in the Hartz was first deter- 

 mined by MM. Murchison and Sedgwick in 1840.* 



Posidonomya Becheri, Gold, 

 Syn. Estheria Becheri. 

 Lower Carboniferous. 



CARBONIFEROUS LIMESTONE IN NORTH AMERICA. 



The coal-measures of Nova Scotia have been described, page 484. 

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

 some bands of marine limestone almost entirely made up of encri- 

 nites, and, in some places, containing shells of genera common to the 

 mountain limestone of Europe. 



In the United States the carboniferous limestone underlies the pro- 



* Trans., Geol. Soc. London, Second Series, vol. vi. p. 228. 



