10 Zoology of Colorado 



Bagdad. The collections obtained by Scudder were very extensive, 

 and were eventually described and figured in large works pub- 

 lished by the United States Geological Survey. The plants were 

 similarly treated by Lesquereux, and the fishes by Cope. Thus 

 this rather out of the way spot, known to comparatively few people 

 in Colorado, became famous in the literature of paleontology, and 

 is referred to in nearly all the text-books of geology. The age of 

 the deposits was long a matter of dispute, and was difficult to 

 settle for two reasons. In the first place the shale rests on a base 

 of metamorphosed rocks, and is nowhere in contact with any of 

 the fossil f erous strata. 1 1 is therefore impossible to secure direct 

 proof that it is earlier or later than any previously known beds. 

 In the second place we still lack remains of mammals, which of 

 all fossils are the most satisfactory for marking time, owing to 

 their comparatively rapid evolution. In spite of these difficulties, 

 it is now generally agreed that the shales belong to the Miocene 

 division of Tertiary time, and are therefore very much later than 

 the oil shales of the Roan Mountains. This opinion has been 

 reached through comparison with deposits of known relative age, 

 and is fortified by other considerations. Thus it is known that dur- 

 ing Miocene time there was continuous land from Asia to what is 

 now Alaska, and the climate was much warmer than at present. 



There was an extensive migration of the old world types into 

 America. It is also known that at a later epoch North and South 

 America, which had been separated, were united by land, and 

 southern animals entered the northern continent. Now the Flor- 

 issant fossils do indicate the presence of old world elements, which 

 so far as we know did not exist in America earlier than the Mio- 

 cene. But there is no clear indication of South American forms, 

 and it appears probable that in the days of Lake Florissant the 

 Isthmus of Panama was still under water. Reasoning of this 

 kind depends upon the gradual accumulation of data, and what 

 at first is suspected, later becomes probable, and eventually may 

 be so well supported that a definite theory can be established. 

 The Florissant problem is still subject to reconsideration from 

 many angles, and every scrap of new information has its value as 

 bearing upon the final solution. 



Scudder's largest work was dated 1890, and his latest con- 

 tribution to the knowledge of Florissant fossil insects appeared in 



