SEA-SERPENTS 197 



second specimen, more complete in all respects, was discovered 

 by Professor Cope's exploring party during an expedition 

 from Fort Wallace, Kansas, in 1871. This specimen he has 

 fully described and figured in Cope's Tertiary Vcrtebrata, 

 1875. It is a very instructive specimen, including fifty of the 

 vertebrae from all parts of the vertebral column, a large part 

 of the cranium, with teeth, as well as important limb-bones. 

 These precious relics were excavated from a chalk "bluff," or 

 high bank. 



In considering the " Age of Eeptiles," we cannot but marvel 

 greatly at the diversity of forms assumed by the various 

 orders of this class, their strange uncouth appearance, their 

 assumption, in some cases, of characters only known at the 

 present day among the mammals, their great abundance, and 

 the perfect state in which their remains have been preserved in 

 the stratified rocks of various parts of the world. And the reader 

 may naturally ask, "How is it that so many types have dis- 

 appeared altogether, leaving us out of a total of at least nine 

 orders, only four, viz. those represented by crocodiles, lizards, 

 snakes, and turtles ? " To such a question we can only answer 

 that the causes of the extinction of plants and animals in the 

 past are not yet known. Climate, geographical conditions, food- 

 supply, competition, with other causes, doubtless operated then 

 as now ; but if there is one clear lesson taught by the record of 

 the rocks, it is this that there has been at work from the 

 earliest periods a Law of Progress, so that higher types, coming 

 in at certain stages, have ousted the lower types, sometimes only 

 partially, sometimes completely. But why the Dinosaurs, for 

 instance, perished entirely, while the crocodiles survived to the 

 present day, no one can yet explain. We can see no reason, 

 however, why such problems as these should not be solved 



