THE 
GEOLOGICAL MAGAZINE. 
No. XV.—SEPTEMBER 1865. 
ORIGINAL ARTICLES. 
——+——_ 
JI. Toe Camprian Rocks OF THE Britisa ISLANDS, WITH ESPECIAL 
REFERENCE TO THE OCCURRENCE OF THIS FORMATION AND ITS 
Fossi_s In IRELAND. 
By Wm. Heruisr Barry, F.LS., F.G.S., &e., 
Acting Palzontologist to the Geological Survey of Ireland. 
| ae term Cambrian (from Cambria, the ancient name of Wales) 
was originally employed by the Rev. Professor Sedgwick to 
include a great series of fossiliferous and other rocks occurring below 
the Bala Limestone in North Wales. Sir Charles Lyell* adopts to 
a certain extent this classification, dividing it into Upper and Lower 
Cambrian. 
Sir R. I. Murchison alludes to this formation as the ‘Cambrian or 
Basement Rocks of the Silurian Region,’ f including under that 
designation those of the Longmynd Hills in Shropshire and their 
equivalents in North Wales. He explains his use of the term Cam- 
brian to be ‘as restricted by the late Sir H. de la Beche, and his 
associates of the Geological Survey, in applying it only to the lowest 
of these sedimentary rocks, which, like those of the Longmynd, 
underlie all the strata with Silurian fossils.’ In accordance with 
this application of the term as being that generally adopted by geo- 
logists, [ propose now to consider it. 
The occurrence of Cambrian, and even perhaps Pre-Cambrian, or 
Laurentian, Rocks in Scotland appears to be well authenticated both 
by Sir R. I. Murchison and other observers; but the exact relations 
of the rocks believed to belong to these older formations in the 
north-west of Scotland and the Hebrides is at present undecided, 
and no fossils have yet been discovered in them. 
The rocks of North Wales referred to the Cambrian formation, on 
* Manual of Elementary Geology (6th edit.), pp. 106, 569, &e. 
fT Siluria (2nd edit.), p. 21, &. 
VOL. II.—NO. XV. cc 
