ces of treatment are merely nominal. Jules Marcou and others
have used _Taconic_ (Taconian) as the equivalent of Cambrian, and C.
Lapworth proposed to apply the same term to the lowest subdivision
only; he had also used "Annelidian" in the same sense. These names are
of historical interest alone.

_Cambrian Rocks._--The lithological characters of the Cambrian rocks
possess a remarkable uniformity in all quarters of the globe. Muds,
sands, grits and conglomerates are the predominant types. In Scotland,
North America and Canada important deposits of limestone occur and
subordinate limestones are found in the Cambrian of central Europe.

In some regions, notably in the Baltic province and in parts of the
United States, the rocks still retain their original horizontality of
deposition, the muds are scarcely indurated and the sands are still
incoherent; but in most parts of the world they bear abundant evidence
of the many movements and stresses to which they have been exposed
through so enormous a period of time. Thus, we find them more
frequently, folded, tilted and cleaved; the muds have become shales,
slates, phyllites or schists, the grey and red sands and conglomerates
have become quartzites and greywackes, while the limestones are very
generally dolomitized. In the Cambrian limestones, as in their more
recent analogues, layers and nodules of chert and phosphatized material
are not wanting.

[Illustration: Distribution of Cambrian Rocks.]

Igneous rocks are not extensively developed; in Wales they form an
important feature and occur in considerable thickness; they are
represented by lavas of olivine-diabase and by contemporaneous tuffs
which are traversed by later granite and quartz felsite. In the Cambrian
of Brittany there are acid lavas and tuffs. Quartz porphyry, diabase and
diorite appear in the Ardennes. In Bohemia, North America and Canada
igneous rocks have been observed.

In China, on the Yang-tse river, a thick deposit has been found full of
boulders of diverse kinds of rock, striated in the manner that is
typical of glacial action. A similar deposit occurs in the Gaisa beds
near the Varanger Fjord in Norway. These formations lie at the base of
the lowest Cambrian strata and may possibly be included in the
pre-Cambrian, though in Norway they are clearly resting upon a striated
floor of crystalline rocks.

_Cambrian Life._--In a general survey of the life of this period, as it
is revealed by the fossils