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BRITISH FOSSILS, STRA.TIGRAPHICALLY ARRANGED. 
Bi' John Moeeis, F.G.S. 
I. PALEOZOIC SYSTEM. 
The Palteozoic System comprises the earliest fossil-bearing strata. 
These have collectively a great thickness, and are of various mineral 
characters, being argillaceous, arenaceous, and calcareous, generally 
indurated, and occasionally metamorphosed. 
As a general rule, these strata appear in the western and north- 
western districts of Britain, and, to a considerable extent, in the mari- 
time districts of Ireland. The rocks of this system contain the chief 
metaliferous workings, as in Cornwall, North Wales, Cumberland, 
Scotland, &c. The upper portion, namely, the Carboniferous, affords 
the chief source of our lead-ores which occur in the limestone of 
Derbyshire, Flintshire, and Cumberland ; and the associated shales and 
sandstones, forming the Coal- Measures, contain the well-known ex- 
tensive deposits of fossil fuel and iron-ore. 
The palfEozoic strata are numerous enough and sufficiently distinct 
among themselves to form several series. The first or lower of these 
comprises the Cambrian and Silurian ; the middle is the Devonian ; 
and the uppermost includes the Carboniferous and Permian. 
1. Lower Palaeozoic Rocks. 
(Cambrian and Silurian.) 
The lower portion of the palaeozoic system' has two great groups of 
rocks; the lower one is named Cambrian by the Rev. Professor 
Sedgwick,— from its great extent in Wales ; — the other is called 
Silurian by Sir Roderick Murchison, on account of the typical strata of 
this group having been worked out by him in the country once in- 
habited by the Silures, — the border-counties of England and Wales, 
where the group is extensively developed. 
