DEVONIAN SERIES IN NORTH DEVON. 
449 
Marine or Devonian Type. —We may now speak of the ma¬ 
rine type of the British strata intermediate between the Car¬ 
boniferous and Silurian, in treating of which we shall find it 
much more easy to identify the Upper, Middle, and Lower 
divisions with strata of the same age in other countries. It 
was not until the year 1836 that Sir R. Murchison and Pro¬ 
fessor Sedgwick discovered that the culmiferous or anthra¬ 
citic shales and sandstones of North Devon, several thousand 
feet thick, belonged to the coal, and that the beds below 
them, which are of still greater thickness, and which, like the 
carboniferous strata, had been confounded under the general 
name “graywacke,” occupied a geological position corre¬ 
sponding to that of the Old Red Sandstone already described. 
In this reform they were aided by a suggestion of Mr. Lons¬ 
dale, who, after studying the Devonshire fossils, perceived 
that they belonged to a peculiar palaeontological type of in¬ 
termediate character between the Carboniferous and Silurian. 
It is in the north of Devon that these formations may best 
be studied, where they have been divided into an Upper, 
Middle, and Lower Group, and where, although much con¬ 
torted and folded, they have for the most part escaped being 
altered by intrusive trap-rocks and by granite, which in 
Dartmoor and the more southern parts of the same county 
have often reduced them to a crystalline or metamorphic state. . 
DEVONIA^^ SERIES IN NORTH DEVON. 
(a.) Sandy slates and schists with fossils, 36 species out of 
110 common to the Carboniferous group (Pilton, Barn¬ 
staple, etc.), resting on soft schists in which fossils are very 
abundant (Croyde, etc.), and which pass down into 
(6.) Yellow, brown, and red sandstone, with land plants (Cy- 
. clopteris^ etc.) and marine shells. One zone, characterized 
by the abundance of cucullsea (Baggy Point, Marwood, 
Sloly, etc.), resting on hard gray and reddish sandstone and 
micaceous flags, no fossils yet found (Dulverton, Pickwell, 
Down, etc.). 
(a.) Green glossy slates of considerable thickness, no fossils 
yet recorded from these beds (Mortenoe, Lee Bay, etc.). 
(b.) Slates and schists, with several irregular courses of lime¬ 
stone containing shells and corals like those of the Plymouth 
Limestone (Combe Martin, Ilfracombe, etc.). 
(a.) Hard, greenish, red, and purple sandstone—no fossils yet 
found (Hangman Hill, etc.). 
(b.) Soft slates with subordinate sandstones—fossils numerous 
at various horizons—Orthis, Corals, Encrinites, etc. (Valley 
of Rocks, Lynmouth, etc.). 
The above table exhibits the sequence of the strata or 
subdivisions as seen both on the sea-coast of the British 
Channel and in the interior of Devon. It will be seen that 
Upper 
Devonian 
OR Pilton 
Group. 
Middle 
Devonian 
OR 
Ilfracombe 
Group. 
>mbe 
rp. [ 
Lower 
Dev^onian j 
OR Lynton j 
Group. 
