statements respecting Sutherland and Bohemia, we have in this
"system" the first appearances of life upon our planet. The animal
remains are chiefly confined to the slate beds, those named from
Bala, in Wales, being the most prolific. Zoophyta, polyparia,
crinoidea, conchifera, and crustacea, {60} are the orders of the
animal kingdom thus found in the earliest of earth's sepulchres. The
ORDERS are distinguished without difficulty, from the general
characters of the creatures whose remains are found; but it is only
in this general character that they bear a general resemblance to any
creatures now existing. When we come to consider specific
characters, we see that a difference exists--that, in short, the
species and even genera are no longer represented upon earth. More
than this, it will be found that the earliest species comparatively
soon gave place to others, and that they are not represented even in
the next higher group of rocks. One important remark has been made,
that a comparatively small variety of species is found in the older
rocks, although of some particular ones the remains are very
abundant; as, for instance, of a species of asaphus, which is found
between the laminae of some of the slate rocks of Wales, and the
corresponding rocks of Normandy and Germany in enormous quantities.

Ascending to the next group of rocks, we find the traces of life
become more abundant, the number of species extended, and important
additions made in certain vestiges of fuci, or sea-plants, and of
fishes. This group of rocks has been called by English geologists,
the Silurian System, because largely developed at the surface of a
district of western England, formerly occupied by a people whom the
Roman historians call Silures. It is a series of sandstones,
limestones, and beds of shale (hardened mud), which are classed in
the following sub-groups, beginning with the undermost: --1,