Geological Society. 401 



strata (dipping under tlie alum-slates above-mentioned, and resting 

 on dark shales, like those which form the base of the limestone) oc- 

 cupy the exact place of the carboniferous limestone in the transverse 

 sections. The group is characterized by dark flinty slate (Kiesel 

 Schiefer) and dark and often fetid thin-bedded limestone, and so 

 closely resembles the culm-limestone series of Devonshire, that the 

 description of one formation might almost serve for the other. Like 

 the culm-limestone, it also contains many Goniatites and Possidonijfi ; 

 and among the latter, the Possidonia Becheri of Devon. It wants, 

 however, the numerous species of mountain limestone fossils of the 

 beds above-noticed, a fact which the authors explain by a reference 

 to a change in all the physical conditions of the deposit. This group, 

 following all the sinuosities of a most contorted country, and some- 

 times doubled back upon itself for many miles together, may be 

 traced by its Kiesel Schiefer and Possidonia schists, and sometimes 

 by its black fetid limestones, to the eastern limit of the chain of older 

 rocks near Bleiwasche and Stadtberge. 



§ 3. Devonian System. — The authors next describe the rocks im- 

 mediately inferior to the carboniferous groups. The mountain lime- 

 stone of Cromfort, above-described, rests on dark-coloured shale, but 

 the descending section is much obscured by overlying deposit. In 

 the long range of the same series, from Elberfeldt to Menden, there 

 are many clear transverse sections, exhibiting in greater or less per- 

 fection the following descending order (1.) Immediately under the 



lower limestone shales are many reddish bands, with calcareous con- 

 cretions, in which the Possidonia and some of the species of the 

 superior groups are still found. (2ndly.) These are succeeded by 

 a well-marked range of psammites and coarse flagstone. (Srdly.) 

 From beneath the psammites rise a series of shales, and bands of 

 psammite of dark colour, with here and there thin courses of inferior 

 limestone, in which we find flattened Goniatites, and shells of a 

 species different from those of the overlying formations, among which 

 especially is noticed the Terehratula aspera of Schlotheim. These 

 are, therefore, considered as forming a part of an inferior system, 

 and the first and second groups of the section may be regarded as 

 made up of beds of passage between the carboniferous system and 

 that which is below it. The sequence here given is compared with 

 the highest beds of the Devonian series, immediately under the culm 

 measures, and with the yellow sandstones of Ireland described bj'^ 

 Mr. Griflith. 



3 a. Lower Limestone of Westphalia, S^c. — Tliis limestone rises 

 immediately from below the third group of the preceding section. 

 Its range; (from tiie neighbourhood of Ratingen, in the valley of the 

 Ilhine, to the confines of Ilessia) is described in detail. Its changes 

 of miiu'ral structure! — its sej)aration \wvo. and there into two zones — • 

 its contraction in one place and its great expansion in another — its 

 enormous flexunis and occasional inversions of position — its re-aj)- 

 pearance at W'arstein and Attendorn, in consequence of such flex- 

 ures, — ail thes(! phainomena are noticed in their turn. As a whole, 

 it lias so great a resemblance to the limestone of South Devon, that 

 Phil. Mag, S. 3. Vol. 1 8. No. 1 1 8. May 1 8i 1 . 2D 



