. Adventures with animals and plants. Biology. PROBLEM 2. We Leiwn of Vrehistoric Livhig Things from Fossils 535. I'n;. 4S5 A Litinbriaii iiiideruiatcr scene. The larij^e anhnal near the center is a giant trilabite. M'hat others can you recognize? (Smithsonian scientific series, inc.) in the latter pait of this second era there is some evidence that life existed, prob- ably simple one-celled plants and animals. The rocks of the third era contain only a few fossils but it seems clear that sea- weeds and various kinds of very simple sea-dwellincT invertebrate animals lived in this third era (Pro
. Adventures with animals and plants. Biology. PROBLEM 2. We Leiwn of Vrehistoric Livhig Things from Fossils 535. I'n;. 4S5 A Litinbriaii iiiideruiatcr scene. The larij^e anhnal near the center is a giant trilabite. M'hat others can you recognize? (Smithsonian scientific series, inc.) in the latter pait of this second era there is some evidence that life existed, prob- ably simple one-celled plants and animals. The rocks of the third era contain only a few fossils but it seems clear that sea- weeds and various kinds of very simple sea-dwellincT invertebrate animals lived in this third era (Proterozoic). It will help to study the diagram, Figure 483. Note that five sixths of the earth's his- tory was already over w hen the fourth era began. But that was far from recent. It was 550,000,000 years ago. The fourth era (Paleozoic). Examina- tion of Figure 483 shows that this, too, was a long era. Much of our continent seems to have been under water in the early periods. The only fossils in the old- est Paleozoic rocks are those of water- dwelling plants and animals. It is be- lieved that there was no soil covering the rocks since no fossils of land-living plants or animals have been found. Seaweeds were plentiful and, judging from the large number of fossils, the oceans and inland waters were teeming with jellyfish and sponges, animals like our modern star- fish, corals of many kinds, and snails. There were more complex invertebrates, too, shrimplike forms. In one early pe- riod of this era (the Cavibrian period) the most common animal type was one which has since disappeared from the earth, the trilobite (try'lo-bite). It is classified in the lobster group (Crustacea). Some spe- cies were two inches long; others reached a size of t\vo feet or more. Trilobites were so numerous and of so many kinds. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations ma
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Keywords: ., bookcentury1900, bookpublisherbostondcheath, booksubjectbiology
