140 How is the Camhrian divided? — Mattheio. 
succession, has lead to this proposal for anewallotment of the 
parts of the Cambrian system. 
If the object in view were merely the arrangement of the 
members of this system which may occur in any particular 
country, the sedimentation, or division into series, in that coun- 
try could be utilized for the purpose, but as the object is a 
classification that will apply generally, other criteria must be 
sought. Among those which have been used are the succes- 
sion of the several faunas and the relationship of the genera in 
each , and the comparative bulk of measures in the several 
parts of the system. These form the basis of the following 
remarks. 
The Cambrian rocks as originally described by Prof. Sedg- 
wick no doubt contained the Ordovician or Lower Silurian as 
well as the strata to which the name has since been restricted. 
These (the Lingula flags, etc.) were also claimed by Sir R. 
Murchison as a part of his Silurian system. In later times 
the conflicting claims of these discoverers have been compro- 
mised by assigning to each his own special domain, and erect- 
ing the disputed territory into a separate system, the Ordovi- 
cian. 
The development of the Cambrian system from its original 
basis in the Lingula flags, etc., received a great impulse from 
the discoveries of Dr. Henry Hicks and the late Mr. J. W. Sal- 
ter in Wales ; and especially in the finding of the Menevian 
fauna in South Wales, by Dr. Hicks, 
In the process of elaborating the Cambrian faunas, the first 
step was the discrimination of the two faunas in the Lingula 
flags in 1853. 
1865. In this year Messrs. Salter & Hicks made known the 
Menevian fauna, and showed the position of the Para- 
doxides beds in Britain. 
1866. In this year the Tremadoc fauna was distinguished in 
South Wales, and fully confirmed in 1872. 
1869. In 1869 Messrs. Hicks and Harkness described the 
great series of red, green and grey slates below the 
Menevian in South Wales, and showed the existence of 
a fauna older than that of the Paradoxides beds but 
with no trilobites. 
Subsequently Dr. Hicks elaborated the Cambrian system into 
seven groups, but showing only four trilobite faunae, the first 
