28 EDWARD WILBER BERRY 



The first land-plants known occur in the Devonian, which is 

 only midway back in the Paleozoic, and the first invertebrate 

 faunas of any representative character occur in the earliest 

 Paleozoic. 



From the figures of ratios given above it is seen that over half 

 of geologic time had elapsed before any recognizable animals or 

 plants are found. This explains the relatively high degree of 

 organization of the earliest known fossils, both animal and vege- 

 table, since more time intervenes between the formation of the 

 earliest recognizable Archeozoic rocks and the appearance of 

 fossil plants in the known record, than intervenes between that 

 time and the present. This situation really holds out the hope 

 that any day we may discover some unmetamorphosed lens of 

 shale in these older rocks that will reveal to us the life of the 

 ages long antecedent to the Cambrian. 



From the high organization and consequent differentiation of 

 the earliest known floras and faunas it is a legitimate conclusion 

 that their ancestors passed through a long antecedent period of 

 evolution. Terrestrial plant life in the oldest records comprises 

 representatives of five phyla of vascular plants, ^ including 

 seed-plants, so that the lost interval represents a longer period 

 of evolutionary activity than the known record down to the 

 present, thus confirming the evidences of chronology derived 

 from physical sources. 



The bulk of the early sediments have been many times sub- 

 jected to the action of epeirogenic and orogenic forces and are 

 consequently so altered that all traces of contained organisms 

 have been obliterated. Moreover terrestrial plants are almost 

 invariably preserved in lacustrine, fluviatile, or palustrine de- 

 posits on the bosoms of the continents or in the estuary and 

 lagoon deposits of the continental margins. True marine de- 

 posits of whatever age rarely contain plants except such as con- 

 tributed to the sea-drift and these are relatively few in number 

 and usually unrecognizable by the time they were buried. 



1 The Pteridophyta or ferns, the Lepidophyta or lepidodendrons and sigil- 

 larias, the Arthrophyta or calamites and their allies, the Pteridospermophyta or 

 seed-ferns, and the Coniferophyta or conifers. 



