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open-grained yellowish psammite; the lower (with many variations 
of structure, and with occasional subordinate calcareous bands) 
abounding in a dull greenish-gray earthy schist, not unlike the 
“‘mudstone” 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 lower 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 
voleanic 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 Terrrain anthraxifera of Professor Dumont 
form a part of the Devonian system, and not a part of the Silurian 
system. 
Lower quartzo-schistose system.—tIn 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 supposed 
analogies of the lower limestone with the mountain limestone of 
England, have been classed with the old red sandstone. Without 
attributing any value whatever to these conglomerates, as terms of 
comparison with English formations, and 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, 
and exhibits the following descending order; (1.) Calcareous shales, 
forming the base of and passing into, the limestone; (2.) Indurated 
shales, alternating with sandstone and flagstone, occasionally of a 
reddish colour; (3.) Sandstone, flagstone, arenaceous slate, quartz- 
ite, &e., gradually passing into a slate formation. The authors re- 
fer to various lists of fossils, and conclude that, though several spe- 
cies are in common with those of the overlying Devonian system, 
yet that as a group they-are distinct: 1st. Because the carboniferous 
species disappear; 2ndly. Because some of the most characteristic 
species of the lower limestone (such as the Strygocephalus Burtini, 
&c.) are wanting; 3rdly. Because new (and Silurian) types begin 
to abound; more especially shales of the genus Prerinea, several 
