482 
ELEMENTS OF GEOLOGY. 
flags, the place of which will be seen in the annexed table. 
By this time Barrande had already published an account of 
a rich collection of fossils which he had discovered in Bo¬ 
hemia, portions of which he recognized as of corresponding 
age with Murchison’s Upper and Lower Silurian, while oth¬ 
ers were more ancient, to which he gave the name of “ Pri¬ 
mordial,” for the fossils were sufficiently distinct to entitle 
the rocks to be referred to a new period. They consisted 
chiefly of trilobites of genera distinct from those occurring 
in the overlying Silurian formations. These peculiar genera 
were afterwards found in rocks holding a corresponding po¬ 
sition in Wales, and I shall retain for them the term Cambri¬ 
an, as recent discoveries in our own country seem to carry 
the first fauna of Barrande, or his primordial type, even into 
older strata than any which he found to be fossiliferous in 
Bohemia. 
The term primordial was intended to express M. Bar- 
rande’s own belief that the fossils of the rocks so called af¬ 
forded evidence of the first appearance of vital phenomena 
on this planet, and that consequently no fossiliferous strata 
of older date would or could ever be discovered. The ac¬ 
ceptance of such a nomenclature would seem to imply that 
we despaired of extending our discoveries of new and more 
ancient fossil groups at some future day when vast portions 
of the globe, hitherto unexplored, should have been thorough¬ 
ly surveyed. Already the discovery of the Laurentian Eo- 
zoon in Canada, presently to be mentioned, discountenances 
such views. 
The following table will show the succession of the strata 
in England and Wales which belong to the Cambrian group 
or the fossiliferous rocks older than the Arenig or Lower 
Llandeilo rocks: 
UPPER CAMBRIAN. 
Tremadoc Slates. (Primordial of Barrande in part.) 
Lingula Flags. (Primordial of Barrande.) 
« 
LOWER CAMBRIAN. 
Menevian Beds. 
Longmynd Group. 
(Primordial of Barrande.) 
(a. Harlech Grits. 
\h. Llanberis Slates. 
UPPER CAMBRIAIS^. 
Tremadoc Slates. —The Tremadoc slates of Sedgwick are 
more than 1000 feet in thickness, and consist of dark earthy 
slates occurring near the little town of Tremadoc, situated 
on the north side of Cardigan Bay, in Carnarvonshire. These 
