How Is the Cmnhrlan divided? — Matthew. 141 
or oldest not having been found by him in IJritian. The groups 
of sediments containing tliese faunas he classified as follows : 
Lower Cambrian. Tliree groups. — Caerfai, Solva and Me- 
nevian. 
Upper Cambrian. Four groups. — Macntwrog, Ffestiniog, 
Dolgelly and Tremadoc. 
It may be well to inquire what there is to support this classi- 
fication of the Cambrian system, before adopting a new one. 
Two principal criteria for determining a question of this 
kind would be the facies and succession of the faunas and the 
bulk of the measures. In applying these tests, we turn our at- 
tention first to Scandinavia, for in no other part of the world 
is there known such a clear, continuous and complete succes- 
sion of Cambrian faunas as in that country. 
Connection eU'.., of the Cambrian faunas. 
Of the several classes of organisms in these faunas, the tri- 
lobites may be taken, as the group which will best show the 
relationship subsisting betM'cen the several faunas, for they 
are the most varied, and were more sensitive to the changing 
conditions of environment than the others. 
In Brogger's admirable work on the Stages 2 and 3 of the 
Pakeozoic rocks of Norway, a table is given which shows the 
succession and range of the species in the Cambrian faunas of 
that country. Then as regards the neighboring kingdom of 
Sweden, Dr. G. Lindstrom's list (1888) of the fo.'^sil faunas of 
the Cambrian and Lower Silurian rocks is complete for the 
several zones of the Cambrian in that country. Combining the 
genera from these sources a full representation of Cambrian 
life in Scandinavia is obtained, so far as relates to the genera 
of the trilobites. 
The first or oldest fauna presents the following genera : 
Olkni:llus(=Mksox.\cis) * Arionellus { = Agraulos.) 
* Ellipsoceph a I us. * A(/n ost us. 
Of these genera one is peculiar and three (marked by an 
asterisk) pass to the next fauna. 
In the second fauna are the genera. 
* Ilarpides Anomocarc. 
Pauadoxides (including Centropleura) 
Llliposcephalus Dolichometopvs 
*Liostyacus (includes Ptychoparia.) 
' Ancuacanthus (c.f. Centropletira?) 
