137 



These were covered, with hard, en- 

 amel-coated scales or bony plates. 

 Some were short and heavy and en- 

 tirely encased in a covering of large 

 bony plates. They were evidently any- 

 thing but pretty and their movements 

 in the water must have been extremely 

 awkward. Others were formed much 

 after our own ideas of fishes. These 

 bore much resemblance to our gar- 

 pikes, the lung fish of the Nile and the 

 lung fish of Australia, and the worth- 

 less dog fish of our own fresh waters. 

 Anglers and fishermen all despise 

 these fishes now, yet in Devonian times 

 the fishes most nearly like them were 

 evidently the most handsome and 

 graceful of all fishes then living. It 

 appears as if fishes in those days did 

 not fight each other. They found 

 abundant sea room and plenty of food 

 in the form of invertebrates. Of course 

 it is quite probable that many fish-like 

 animals existed at this time, but pos- 

 sessing no hard parts and were not 

 preserved as fossils ; these could not be- 

 come 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 in- 

 creased, the seasons, such as they were 

 then, became more marked ; many in- 

 land 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 resem- 

 blance 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 re- 

 tained their prominence to the close 

 of the Carboniferous. The slow-mov- 

 ing, heavily plated ganoids passed 

 away. They ruled during the De- 

 vonian age, but could not suit them- 

 selves to the new conditions at begin- 

 ning of the Carboniferous. While 

 fishes were numerous and large in the 

 Devonian, throughout the Carbonif- 

 erous 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 ani- 

 mals. At the close of the Carbonifer- 

 ous 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 ne\Y era in the geological his- 

 tory 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 repre- 

 sented by new forms more like those 

 now living. The geological age fol- 

 lowing the Carboniferous is the Trias- 

 sic. With this, age began our modern 

 sharks and fishes. They did not be- 

 come abundant until the Jurassic and 

 Cretaceous. All of the earlier sharks 

 had strong spines in front of each dor- 

 sal fin and broad teeth made for crush- 

 ing. 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. 

 These sharks, with pointed teeth, but 

 rounded on the edges, commenced 

 back in the Carboniferous. During 

 the Triassic the sharks, with lancet- 



