i82 THE CHAIN OF LIFE. 



picture. It represents a time which actually existed, when 

 that comparatively low, brutal, and insensate type of existence 

 represented by the modern crocodiles and alligators was 

 supreme in the world. The duration of these creatures was 

 long, and in watching the progress of creation, they would have 

 seemed the permanent inhabitants of the earth. Yet all have 

 perished, and their modern successors, except a few large 

 species existing in the warmer climates, have become subject 

 to the more recently introduced Mammalia. 



How did the ancient reptile aristocracy perish? We are 

 ignorant of the details of the catastrophe, but their final dis- 

 appearance and replacement by the more modern fauna was 

 connected with a great continental suosidence in the Creta- 

 ceous age, and with changes of climate and conditions pre- 

 ceding and subsequent to it. Yet the struggle for continued 

 dominion was hard and protracted ; and toward its close some 

 of the champions of the reign of reptiles were the greatest 

 and most magnificent examples of the type ; as if they had 

 risen in their might to defy approaching ruin. Thus some of 

 the most stupendous forms appear in the later Cretaceous 

 after the great subsidence had made progress and almost at- 

 tained its consummation. Like the antediluvian giants, chey 

 were undismayed even when the land began to sink beneath 

 their feet ; and for them there was no ark of deliverance. 



