THE EOZOIC ERA 47 
The derivations of these names give you a clue 
to the Eras they represent. Eozoic rocks contain 
fossils of some of the earliest forms of life, while 
Cainozoic deposits include remains of recent forms 
of life. 
For purposes of classification and study, the Eras 
are divided into Periods, which I shall now set down 
in tabular form, giving you typical fossils of each 
Period, and some other details. 
THe Eozoic Era. 
Canada, etc. 
| | | 
| Estimated | . 
| Period. (Thickness | Nature of Strata. bia sidida toss | 
| | in Feet. 
Archean 50,000 | Metamorphosed | Shropshire, War- | 
(Greek archaios | Igneous Rocks, | wickshire, Worces- 
= ancient) | Schists, Quartz- | tershire, Leicester- 
ites, Crystalline | shire, North-West 
| Limestones,Con- | Highlands of Scot- 
| glomerates, Sand- land, Finland, 
| stones, Shales Scandinavia, 
| 
| 
| 
\ wi 
Se et 
The lower Archzean rocks contain no fossils ; they 
consist largely of metamorphosed igneous and sedi- 
mentary rocks, but the absence of fossils must not 
be taken as evidence of there being no living 
creatures at the remote age they represent. 
Creatures of lower Archean date may have been very 
low in the scale of life, and have had no skeleton to 
endure, or if they had skeletons, the deposits in 
which they were laid have been subjected to so 
much compression and change that the remains 
