Lake Ladoga. At the base is the so-called "blue clay"
(really greenish) with ferruginous sandstones and with a fucoidal
sandstone at its summit. This division is the equivalent of the Lower
Cambrian. Above the fucoidal sandstone an important break appears in
the system, for the _Paradoxides_ and _Olenus_ divisions are absent.
The upper members are the "Ungulite grit" and about 20 ft. of
Dictyonema shale. Cambrian rocks have been traced into Siberia (lat.
71 deg.) and on the island of Vaigatch.

_Central Europe._--Besides the Bohemian region previously mentioned,
Cambrian rocks are present in Belgium and the north of France, in
Spain and the Thuringer Wald. In the Ardennes the system is
represented by grits and sandstones, shales, slates and quartz
schists, and includes also whet slates and some igneous rocks. A.
Dumont has arranged the whole series (_Terrain ardennais_) into three
systems, an upper "Salmien," a middle "Revinien" and a lower
"Devillien," but J. Gosselet has subsequently proposed to unite the
two lower groups in one.

_France_.---In northern France Cambrian rocks, mostly purple
conglomerates and red shales, rest with apparent unconformability upon
pre-Cambrian strata in Brittany, Normandy and northern Poitou. In the
Rennes basin limestones--often dolomitic--are associated with
quartzites and conglomerates; silicious limestones also occur in the
Sarthe region. Farther south, around the old lands of Languedoc,
equivalents of the two upper divisions of the Cambrian have been
recorded; and the uppermost members of the system appear in Herault.
Patches of Cambrian rocks are found in the Pyrenees.

In _Spain_ slates and quartzites, the slates of Rivadeo, more than
9000 ft. thick, are followed by the middle Cambrian beds of La Vega,
thick quartzites with limestone, slates and iron ores. Cambrian rocks
occur also in the provinces of Seville and Ciudad-Real. Upper Cambrian
strata have been found in upper Alemtejo in Portugal.

In _Russian Poland_ is a series of conglomerates, quartzites and
shales; Some of the beds yield a _Paradoxides_ fauna.

In the _Thuringer Wald_ are certain strata, presumably Cambrian since
the uppermost beds contain the _Euloma-Niobe_ fauna.

_Sardinia_ contains both middle and upper Cambrian. The Cambrian
system is represented in the Salt Range of India by the Neobolus or
Khussack beds, which may possibly belon