hard parts and were not preserved as fossils; these could not become at all important for the sea was too full of large animals of all classes which were so well protected with a coat of mail and so hostile that those less favorably situated could not exist in any great numbers. At the close of the Devonian many changes took place. The rocks of this formation, which now form a portion of the earth's surface, rose out of the water, the land area thus considerably increased, the seasons, such as they were then, became more marked; many inland seas were formed. These changes were more or less gradual, but not so much so that the fishes living then could not suit themselves to the new conditions. Those fishes which had flourished for generations had become accustomed to easy living and certain fixed ways, could not adapt themselves to changing conditions, and so became extinct. The Pteraspids, the earliest forms to appear; the Pterichthys, in fact, all forms which bear any resemblance to our present lampreys, or which may prove a close relative of the earlier ganoids, became extinct at close of the Devonian. The early Chimeras which flourished from close of Silurian also became extinct. Many ganoids became extinct, but other ganoids came into existence to take their places. The ganoids most nearly like our modern sturgeons increased during the last of the Devonian and retained their prominence to the close of the Carboniferous. The slow-moving, heavily plated ganoids passed away. They ruled during the Devonian age, but could not suit themselves to the new conditions at beginning of the Carboniferous. While fishes were numerous and large in the Devonian, throughout the Carboniferous they began to decline. By this time the land area had much increased, land plants became very abundant, there were immense forests of tropical vegetation, great swamps and peat bogs--all of which later sank below sea level--became covered up and changed into coal. Immense lizards lived in these forests and along the sea shores; these were the first land animals. At the close of the Carboniferous great changes took place; greater changes than at any time since the close of the Archaean. So marked were the changes at this time that it marks a new era in the geological history of the earth. All preceding the close of the Carboniferous is regarded as ancient geology; all since then as modern geology. It was at this time that plants and animals were represented by new forms more like those now living. The geological age following the Carboniferous is the Triassic. With this age began our modern sharks and fishes. They did not become abundant until the Jurassic and Cretaceous. All of the earlier sharks had strong spines in front of each dorsal fin and broad teeth made for crushing. One form of these known as Cestracionts were very abundant till the end of the Cretaceous. In the early Triassic they began to decline and the sharks, with pointed teeth, increased.