CHAPTER XVI 

 CHELONIA 



No order of reptiles of the past or present is more sharply and 

 unequivocally distinguished from all others than the Chelonia 

 or Testudinata. No order has had a more uniformly continuous 

 and uneventful history. None now in existence has had a longer 

 known history, and of none is the origin more obscure. The first 

 known members of the order, in Triassic times, were turtles in all 

 respects, as well or nearly as well adapted for their peculiar mode 

 of life as are those now living, and were they now living they would 

 attract no especial attention from the ordinary observer and but 

 little from the naturalist. From time to time some have gone 

 after better things, and have come to grief, but the main line has 

 remained with fewer improvements, fewer evolutional changes, 

 than any other group of higher vertebrates. The turtles seem 

 very early to have adapted themselves so well to their peculiar 

 mode of life, to have intrenched themselves so thoroughly in their 

 own province, that no other creatures have been able to overcome 

 them, or to drive them from it. The remains of no other air- 

 breathing vertebrates are so omnipresent in the rocks as those of 

 the turtles; they may be expected wherever fossils of air-breathing 

 animals are found, though unfortunately often only in scattered 

 and broken fragments. The loose union of their skeletal bones 

 and their general habits of life in shallow waters left their bodies 

 as food for scavengers, or for dismemberment by the tides and 

 currents. 



Relationships with other reptiles they really have none. Some 

 have thought that the plesiosaurs were their first cousins, others 

 the Placodontia, an indeterminate group of extinct reptiles usually 

 placed with the Anomodontia. But their relationship with neither 

 of these is closer than with the crocodiles, dinosaurs, or ptero- 

 dactyls. They are the only reptiles that we know, besides the 



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