^59:1.18 ¶ The marine life was much alike the world over and consisted of the seaweeds, one-celled organisms, simple sponges, trilobites, and other crustaceans — shrimps, crabs, and lobsters. 3,000 varieties of brachiopods appeared at the close of this period, only 200 of which have survived. These animals represent a variety of early life which has come down to the present time practically unchanged.

^59:1.19 But the trilobites were the dominant living creatures. They were sexed animals and existed in many forms; being poor swimmers, they sluggishly floated in the water or crawled along the sea bottoms, curling up in self-protection when attacked by their later appearing enemies. They grew in length from 5 cm to 30 cm and developed into four distinct groups: carnivorous, herbivorous, omnivorous, and “mud eaters.” The ability of the latter group largely to subsist on inorganic matter — being the last multicelled animal that could — explains their great increase and long survival.

^59:1.20 This was the biogeologic picture of Urantia at the end of that long period of the world’s history, embracing 50,000,000 years, designated by your geologists as the Cambrian.

2. THE FIRST CONTINENTAL FLOOD STAGE

THE INVERTEBRATE-ANIMAL AGE

^59:2.1 The periodic phenomena of land elevation and land sinking characteristic of these times were all gradual and nonspectacular, being accompanied by little or no volcanic action. Throughout all of these successive land elevations and depressions the Asiatic mother continent did not fully share the history of the other land bodies. It experienced many inundations, dipping first in one direction and then another, more particularly in its earlier history, but it does not present the uniform rock deposits which may be discovered on the other continents. In recent ages Asia has been the most stable of all the land masses.

^59:2.2 ¶ 350,000,000 years ago saw the beginning of the great flood period of all the continents except central Asia. The land masses were repeatedly covered with water; only the coastal highlands remained above these shallow but widespread oscillatory inland seas. Three major inundations characterized this period, but before it ended, the continents again arose, the total land emergence being 15% greater than now exists. The Caribbean region was highly elevated. This period is not well marked off in Europe because the land fluctuations were less, while the volcanic action was more persistent.

^59:2.3 ¶ 340,000,000 years ago there occurred another extensive land sinking except in Asia and Australia. The waters of the world’s oceans were generally commingled. This was a great limestone age, much of its stone being laid down by lime-secreting algae.

^59:2.4 A few million years later large portions of the American continents and Europe began to emerge from the water. In the Western Hemisphere only an arm of the Pacific Ocean remained over Mexico and the present Rocky Mountain regions, but near the close of this epoch the Atlantic and Pacific coasts again began to sink.

^59:2.5 ¶ 330,000,000 years ago marks the beginning of a time sector of comparative quiet all over the world, with much land again above water. The only exception to this reign of terrestrial quiet was the eruption of the great North American volcano of eastern Kentucky, one of the greatest single volcanic activities the world has ever known. The ashes of this volcano covered 193 km² to a depth of 4.5-6 m.

^59:2.6 ¶ 320,000,000 years ago the third major flood of this period occurred. The waters of this inundation covered all the land submerged by the preceding deluge, while extending farther in many directions all over the Americas and Europe. Eastern North America and western Europe were 3-4.5 km under water.

^59:2.7 ¶ 310,000,000 years ago the land masses of the world were again well up excepting the southern parts of North America. Mexico emerged, thus creating the Gulf Sea, which has ever since maintained its identity.

^59:2.8 The life of this period continues to evolve. The world is once again quiet and relatively peaceful; the climate remains mild and equable; the land plants are migrating farther and farther from the seashores. The life patterns are well developed, although few plant fossils of these times are to be found.

^59:2.9 ¶ This was the great age of individual animal organismal evolution, though many of the basic changes, such as the transition from plant to animal, had previously occurred. The marine fauna developed to the point where every type of life below the vertebrate scale was represented in the fossils of those rocks which were laid down during these times. But all of these animals were marine organisms. No land animals had yet appeared except a few types of worms which burrowed along the seashores, nor had the land plants yet overspread the continents; there was still too much carbon dioxide in the air to permit of the existence of air breathers. Primarily, all animals except certain of the more primitive ones are directly or indirectly dependent on plant life for their existence.

^59:2.10 The trilobites were still prominent. These little animals existed in tens of thousands of patterns and were the predecessors of modern crustaceans. Some of the trilobites had from 25 to 4,000 tiny eyelets; others had aborted eyes. As this period closed, the trilobites shared domination of the seas with several other forms of invertebrate life. But they utterly perished during the beginning of the next period.

^59:2.11 Lime-secreting algae were widespread. There existed thousands of species of the early ancestors of the corals. Sea worms were abundant, and there were many varieties of jellyfish which have since become extinct. Corals and the later types of sponges evolved. The cephalopods were well developed, and they have survived as the modern pearly nautilus, octopus, cuttlefish, and squid.

^59:2.12 There were many varieties of shell animals, but their shells were not then so much needed for defensive purposes as in subsequent ages. The gastropods were present in the waters of the ancient seas, and they included single-shelled drills, periwinkles, and snails. The bivalve gastropods have come on down through the intervening millions of years much as they then existed and embrace the mussels[3], clams, oysters, and scallops. The valve-shelled organisms also evolved, and these brachiopods lived in those ancient waters much as they exist today; they even had hinged, notched, and other sorts of protective arrangements of their valves.

^59:2.13 ¶ So ends the evolutionary story of the second great period of marine life, which is known to your geologists as the Ordovician.

3. THE SECOND GREAT FLOOD STAGE

THE CORAL PERIOD — THE BRACHIOPOD AGE

^59:3.1 300,000,000 years ago another great period of land submergence began. The southward and northward encroachment of the ancient Silurian seas made ready to engulf most of Europe and North America. The land was not elevated far above the sea so that not much deposition occurred about the shore lines. The seas teemed with lime-shelled life, and the falling of these shells to the sea bottom gradually built up very thick layers of limestone. This is the first widespread limestone deposit, and it covers practically all of Europe and North America but only appears at the earth’s surface in a few places. The thickness of this ancient rock layer averages about 300 m, but many of these deposits have since been greatly deformed by tilting, upheavals, and faulting, and many have been changed to quartz, shale, and marble.