Parr Il. Scor.i.§1.) CAMBRIAN. | | 647 
PART JIl.—Pavzozotc. 
Under the general term Paleozoic or Primary are now in- 
cluded all the older sedimentary formations containing organic re- 
mains, up to the top of the Permian system. These rocks consist 
mainly of sandy and muddy sediment with occasional intercalated 
zones of limestone. They everywhere bear witness to comparatively 
shallow water and the proximity of land. Their frequent alterna- 
tions of sandstone, shale, conglomerate, and other detrital materials, 
their abundant rippled and sun-cracked surfaces, marked often with 
burrows and trails of worms, as well as the prevalent character of 
their organic remains, show that they must have been deposited in 
areas of slow subsidence, bordering continental or insular masses of 
land. As regards the organisms of which they have preserved the 
casts, the Palzozoic rocks, as far as the present evidence goes, may 
be grouped into two divisions—an older and a newer :—the former 
(from the base of the Cambrian to the top of the Silurian system) 
distinguished more especially by the abundance of its graptolitic, 
trilobitic, and brachiopodous fauna, and by the absence of vertebrate 
remains; the latter (from the top of the Silurian to the top of the 
Permian system) by the number and variety of its fishes and 
amphibians, the disappearance of graptolites and trilobites, and 
the abundance of its cryptogamic terrestrial flora. 
Section I.—Cambrian. 
§1—General Characters. 
In those regions of the world where the relations of the Archean 
to the oldest Paleozoic rocks are most clearly exposed and have 
been most carefully studied, a more or less marked unconformability 
has been observed between the two series. Such a break points 
no doubt to the lapse of a vast interval of time during which the 
Archean formations, after suffering much crumpling and meta- 
morphism, were ridged up into land and were then laid open to 
prolonged denudation. These changes seem to have been more 
especially prevalent in the northern part of the northern hemisphere. 
At all events there is evidence of extensive upheaval of land in the 
north-west of Europe and across the northern tracts of North 
America prior to the deposit of the earliest remaining portions of the 
Paleozoic formations. These strata indeed were derived from the 
degradation of that northern land, and we may form some idea of its 
magnitude from the enormous piles of sedimentary rock which have 
been formed out of its waste. To this day much of the land in the 
boreal tracts of the northern hemisphere still consists of Archean 
gneiss. We cannot affirm that the primeval northern land was 
lofty; but if it was not, it must have been subjected to repeated 
renewals of elevation, to compensate for the loss of height which it 
