Geological Society. 403 



the descending order is unequivocal. The passage downwards is 

 sometimes effected by flagstones, with bands of shale, containing 

 thin calcareous courses. In other places, the shales are more abun- 

 dant, occasionally becoming much indurated ; and in the range to- 

 wards the north-east (for example, near Meschede) this group be- 

 comes greatly expanded, and contains many quarries of roofing-slate, 

 with a true oblique cleavage. This part of the series is compared 

 with the shales under the Eifel limestone, and with the Wissenbach 

 slates, which underlie the Devonian limestone series of Dillenburg. 

 The great difference in the development of this group produces a 

 great difference in the fossils, but on the whole, they are regarded 

 as forming a passage between the Devonian and Silurian types. A 

 list of fossils is subjoined, and the authors regard the numerous Go- 

 niatites as rather connecting the group with the overlying Devonian 

 rocks; while the trilobites and orthoceratites, &c., some of which 

 cannot perhaps be distinguished from known Silurian fossils, seem 

 to link it to the Silurian system. 



Below the preceding comes a group of vast thickness, composed 

 of earthy schistose beds, passing on one hand into shale, on the other 

 into coarse slate, and alternating indefinitely with bands of psammite, 

 sometimes passing into coarse arenaceous flagstone, sometimes into 

 thick beds of sandstone. Nearly throughout are occasional obscure 

 vegetable impressions, and in the upper part are courses of lime- 

 stone and calcareous bands, with innumerable impressions of fossils. 

 In the lower part, the limestone bands seem gradually to disappear, 

 and the whole passes into a formation of graywacke and graywacke 

 slate, in some rare instances producing a good roofing-slate. For many 

 miles south of the undisturbed range of the lower Westphalia lime- 

 stone, the prevailing dip is about north-north-west. The country 

 round Siegen is regarded as a kind of dome of elevation, composed 

 of the lower part of this series ; for still further south the dip is re- 

 versed to the south-south-east ; and in a traverse from Siegen to the 

 Taunus, across the strike (a distance of about fifty miles), the same 

 dip is continued, with very few interruptions. Considering their 

 high inclination, this fact seems to give an almost incredible thick- 

 ness to the deposits in question. But the vertical sections do not 

 give the order of superposition ; for at Dillenburg, and on the Lahn, 

 two great Devonian troughs are brought in among the older strata, 

 without any general change of dip ; and if we accepted the vertical 

 sections as the sole proofs of superposition, we must place the Devon- 

 ian and a part of the carboniferous series under the chain of the 

 Taunus. The authors therefore endeavoured to apply the method of 

 Professor Dumont, and found their results confirmed by the sections 

 of the lower Lahn. 



Many other local details are given, and the authors having deter- 

 mined the g(;ometrical jjosition of the great mineral masses, next at- 

 tempt to define their age from their fossils. In the arenaceous and 

 calcareous grouj* under the lower Westphalia linustone, many spe- 

 cies of the genus Pterinea (Cioldfuss), Ilonialonotus, Orthis, &c. &c., 

 begin to prevail. Along with these are forms at present unknown 



2D2 



