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species of Orthis, the Homalonotus Knightii, Calymene Blumenbaehii, 
&e. They further remark, that the species of Silurian fossils which 
appear in the Eifel lists are mostly derived from the lower shales, 
which are regarded as beds of passage. Along with known Silu- 
rian fossils there occur also (as remarked in deposits under the 
Westphalian limestone, Part I.) many other fossils, Delthyris mi- 
croptera and D. macroptera, &c., in great abundance. The lower 
quartzo-schistose rocks of Professor Dumont are therefore placed 
in the Silurian system, but without any attempt to subdivide it into 
distinct portions analogous to those of England. And as there is 
no well-defined separation between this system and the overlying 
Devonian, still less is there any well-defined separation between its 
lower limits and the central slate rocks of the Ardennes. 
The slate country of the Ardennes is subdivided into three groups 
of slate rocks,—Upper, Middle, and Lower. All the fossils ob- 
tained by the authors from the upper group are of Silurian types. 
From the middle and lower groups they obtained no fossils: but as 
all the groups are linked together, and the upper is placed by its 
fossils in the lower part of the Silurian system, they assign the two 
lower groups to the upper Cambrian system. They then enter on 
some mineralogical details connected with the structure of the slates 
of the Ardennes; and among the crystalline beds of the lowest 
group (which they regard as only an altered portion of that which 
is next superior), point out some examples of slates derived from a 
cleavage transverse to the beds, and intersected by a true second 
cleavage plane, a rare phenomenon among the slates of England; 
but noticed by the authors among some rocks on the south coast of 
Devon and the north coast of Cornwall. 
§ 2. Formations between the Hifel and the Hundsruck.—Left bank 
of the Rhine, c.—Crossing the strike of the beds from the Eifel to 
the Moselle, by several distinct traverses, the authors met with the 
same series of deposits in descending order: viz. Ist. Calcareous 
shales; 2nd. Arenaceous flagstones and shale; the upper part fre- 
quently exhibiting a reddish tinge, and with portions more or less 
caleareous, and the lower part passing into a great formation of 
arenaceous flagstone, indurated slate and coarse slate, and ocvasion- 
ally of fine quartzite. The series is here and there highly fossili- 
ferous, containing several species of Pterinzea, Delthyris; Orthis, &c., 
occasionally presenting obscure impressions of plants, and casts of a 
large Homalonotus, of a Silurian species. The sequence, deter- 
mined more by the symmetrical position of the great mineral masses 
than by direct superposition, as seen in vertical sections, gradually 
passes into rocks of a more decidedly slaty structure, and almost 
without fossils. Passing to the right bank of the Moselle, and in 
the same way making traverses through the chain of the Hunds- 
ruck (which is elevated on the line of strike, 7. e. east-north-east), 
they again had an ascending series, and thence concluded that the 
whole chain was only a portion of the great system under the Eifel 
limestone in an altered form. ‘The Silurian fossils discovered among 
the crystalline quartzites and schists of the chain (e. g. one or two 
