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 Vertebrata, 
1875. It is a very instructive specimen, including fifty of the 
vertebree 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 Reptiles,’ 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 
