Geological Society. 4-05 



considerable part of its south-eastern boundarj' it is inverted, so as 

 to dip under the older formations ; but on a part of its northern 

 boundary the older formations emerge in their regular order. 



The upper limestone of the second division is undoubted moun- 

 tain limestone. The only question, then, is respecting the equiva- 

 lents of the three lower divisions of the Terrain Anthraxifere, which 

 are, by Professor Dumont, respectively classed with the Ludlow 

 rock, Wenlock limestone, and Caradoc sandstone formations. This 

 classification is not accepted by the authors, for reasons stated in 

 detail. 



The upper quartzo-schistose system is separable at two parts very 

 different from one another : the higher, often characterized by an 

 open-grained yellowish psaramite ; the lower (with many variations 

 of structure, and with occasional subordinate calcareous bands) 

 abounding in a dull greenish-gray earthy schist, not unlike the 

 " raudstone " of the Ludlow rocks. But the higher grits and psam- 

 mites pass insensibly into the bottom beds of the upper limestone 

 (mountain limestone), and contain a series of fossils so near the 

 carboniferous type, that it is difficult to draw a line between the 

 two deposits ; and the lower earthy schists do not contain (among 

 the specimens brought away by the authors) one single species 

 found in the Ludlow rock. 



The lotver limestone of the second division is then described in 

 detail, both as seen in Belgium and the Eifel. The authors dwell 

 some time on the remarkable association of the Eifel dolomites with 

 volcanic rocks of different ages : but they contend that the disloca- 

 tion and contortions of the older strata, and their changes of mine- 

 ral structure, are not generally due to the more recent igneous erup- 

 tions. A comparison of the lists of fossils from the Eifel and lower 

 Belgian limestone, show that they belong to a group identical with 

 that of the lower limestone of Westphalia and the limestone of Paf- 

 frath, and that they present the closest analogies with the fossils 

 derived from the limestones of South Devon ; some of the most 

 abundant species, both of shells and corals, being identical in all 

 the localities. Hence the authors conclude, that the second and 

 third members of the Terrain anthraxifere of Professor Dumont 

 form a part of the Devonian system, and not a part of the Silurian 

 system. 



Lower quartzo-schistose system. — In Belgium it is harder and more 

 quartzose than the upper division, and also of more varied mineral 

 structure ; and in its upper portion contains some thick beds of 

 conglomerate, which, from their mineral structure and the sujiposed 

 analogies of the lower limestone with the mountain limestone of 

 England, have been classed witii the old red sandstone. Without 

 attributing any value whatever to these conglomerates, as terms of 

 comparison with English formations, aiul regarding them only as 

 mineral accidents, the authors place them near the base of the De- 

 vonian system, and consequently near the lower limit of the old red 

 sandstone. 



In the Eifel, the system is better developed and more fossiliferous, 



