|
P < | and slates. | (Famennien). |
E | | Pickwell Down group. | Red and grey slates with |
R | | Dark slates and grits. | tuffs. |
. | | Morte slates (?). | Chudleigh goniatite limestone |
\ | | Petherwyn beds (Frasnien). |
M +-----------------------------+-------------------------------+
I / | Ilfracombe slates with | Torquay and Plymouth |
D | | lenticles of limestone. | limestones and Ashprington |
D < | Combe Martin grits and | volcanic series. (Givetien |
L | | slates. | and Eifelien.) |
E | | | Slates and limestones of |
. \ | | Hope's Nose. |
+-----------------------------+-------------------------------+
L / | Hangman grits and slates. | Looe beds (Cornwall). |
O | | Lynton group, grits and | Meadfoot, Cockington and |
W < | calcareous slates. | Warberry series of slates |
E | | Foreland grits and slates. | and greywackes. (Coblentzien |
R | | | and Gedinnien.) |
. \ +-----------------------------+-------------------------------+

The fossil evidence clearly shows the close agreement of the Rhenish
and south Devonshire areas. In north Devonshire the Devonian rocks
pass upward without break into the Culm.

_North America._--In North America the Devonian rocks are extensively
developed; they have been studied most closely in the New York region,
where they are classified according to Table IV.

The classification below is not capable of application over the states
generally and further details are required from many of the regions
where Devonian rocks have been recognized, but everywhere the broad
threefold division seems to obtain. In Maryland the following
arrangement has been adopted--(1) Helderberg = Coeymans; (2) Oriskany;
(3) Romney = Erian; (4) Jennings = Genesee and Portage; (5) Hampshire
= Catskill in part. In the interior the Helderbergian is missing and
the system commences with (1) Oriskany, (2) Onondaga, (3) Hamilton,
(4) Portage (and Genesee), (5) Chemung.

The Helderbergian series is mainly confined to the eastern par