X 
ABBREVIATIONS 
PALEOZOIC SERIES. 
Permian Group. 
Mag.L. Magnesian Limestone, gypseous marls, &c. 
Carboniferous Group. 
L.R.S, Lower New Red. 
C.M. Coal-measures. 
C.L. Carboniferous Limestone, including the Yoredale and Scar limestones of 
Yorkshire, shales, &c. 
Devonian Group*. 
O.R.S. Old Red Sandstone. 
Dev. Devonian shales and limestones. 
Silurian Group. 
(U.Sil.) Upper Silurian, 
U.Lud. Upper Ludlow. 
Ay.L. Aymestry Limestone. 
L.Lud. Lower Ludlow. 
Wen.L. Wenlock or Dudley Limestone. 
W.Sh. Wenlock Shale. 
(L.Sil.) Lower Silurian or Cambrian^. 
Car. Caradoc Sandstone, including the Horderley and May Hill rocks. 
L.Fl. Llandeilo and Builth Flags. 
* Although under the term Devonian are comprehended many localities, it is very pro- 
bable, as suggested by Mr. Daniel Sharpe, that the strata may be of different ages. I 
have the permission of that gentleman for inserting the following proposed arrangement 
of the Devonian beds : — 
Carboniferous Series — down to the limestone containing Posidonomya ; South Pe- 
therwin, Tintagel, Fowey, Barnstaple, Pilton and Brushford. 
Devonian Series — all the South Devon and Cornwall localities, except South Petherwin 
and Tintagel. 
North Devon Series — (probably Upper and Middle Silurian) Croyde, Baggy Point, 
Marwood, Ilfracombe, Combe Martin, Linton, &c. 
The North Devon shells are older than the South Devon ; the Marwood shells 
are mostly Upper Ludlow species ; the Linton shells probably Middle or Lower Silu- 
rian. The difficulty is with those shells quoted from Baggy Point and Croyde, which re- 
quire more accurate localities to be given in order to form an opinion to which series 
they belong. 
t The researches of Prof. Sedgwick on tbe slate rocks of North Wales have shown that 
there is but one fossiliferous system older than the Wenlock shale. In the district de- 
scribed by Mr. Murchison these rocks have been subdivided into Caradoc sandstone and 
Llandeilo flags, but at present it has been found impossible to apply a similar subdivision 
to the greater portion of the rocks of this region. This remark is also applicable to the 
rocks of South Wales and Cumberland. 
