for unknown genera- 

 tions to tell their 

 humble but not in- 

 significant tale of 

 what has been. To 

 lose or destroy them 

 is like removing a 

 brick from some 

 splendid building; 

 the building will not 

 fall, but the offense 

 is intolerable. 



Perhaps the great- 

 est importance of the 

 Florissant deposit 

 lies in the fact that 

 so many species 

 (more than a thou- 

 sand described) of 

 insects and plants 

 have been found. 

 The great number of 

 forms of life known 

 enables us to recon- 

 struct a picture of 

 the period, and to 

 draw conclusions 

 from the absence as 

 well as the presence 

 of certain groups. 



Florissant is, in 

 effect, a sort of Mio- 

 cene Pompeii, afford- 

 ing us an insight into 

 the past conditions 

 which few deposits 

 in the whole world 

 can give. From it, 

 we may even reason 

 about conditions in 

 remote parts of the 

 world. Thus, the 

 presence of certain characteristic Old 

 World forms of life suggests that land 

 was, or had recently been, continuous 

 between Asia and America; the absence 

 of a distinct South American element 



These fossil leaves are believed to belong to the family Proteaceae, plants which 

 today are found only in countries of the southern hemisphere. Naturalists have 

 speculated as to land bridges across which these plants might have come, but dis- 

 covery of them in the Colorado shales, showing that they once existed in the north 

 temperate zone, has changed the nature of these speculations. The leaves above 

 are strikingly like those of the modern greenhouse plant GreviUen robiisia 



Dragon fly {Phenacolestes) found in the Florissant shales, belonging to a genus 

 now extinct 



indicates that the Isthmus of Panama 

 was still under water. These geograph- 

 ical changes can be demonstrated to have 

 occurred, using quite other evidence; and 

 if it appears that the Florissant beds were 



447 



