FOSSIL FAUNA AND FLORA OF THE FLORISSANT SHALES l6l 



periods are generally such as run through the entire Tertiary series, 

 or, in certain cases, due to mere mistakes. Lesquereux, being most 

 familiar with fossil floras, made comparison with them, but the more 

 one works upon the plants, the more one is impressed with their modern 

 facies, and in many instances with the extremely close resemblance 

 to types still hving in the Rocky Mountains. 



That the deposits . are not later than Miocene, will be generally 

 admitted; for in spite of all resemblances to recent forms, there are 

 plenty of proofs that a long time has elapsed since the deposits were 

 formed. Indeed, argument from this side of the case would be super- 

 flous. With regard to the cUmate prevailing when the Florissant 

 biota lived, it may be said that it was undoubtedly moister and warmer 

 than that of the present day. As has been several times remarked, 

 it seems to have resembled that of our southern states ; but not, I think, 

 the most southern ones. We do not know what elevation of the range 

 may have taken place since the Florissant epoch ; but it may be doubted 

 whether the warmer climate was wholly or primarily due to a lower 

 altitude, for it is well known that the whole continent enjoyed mild 

 or warm temperatures during the Miocene, even far north. ^ Having 

 in view the known Miocene flora of the lowlands in this latitude, 

 it certainly appears that that of Florissant was semialpine or boreal 

 in character; especially since a critical examination of the material 

 and hterature indicates that several of the apparently subtropical 

 species are wrongly credited to it, or are very doubtfully of the genera 

 to which they have been assigned. Even some of the apparent excep- 

 tions confirm the view just stated. Thus Weinmannia, today a neo- 

 tropical genus, is represented by excellent material at Florissant; but 

 on turning to Grisebach's Flora 0} the British West Indian Islands, 

 I find that Weinmannia in Jamaica is "common on the summits of 

 the Blue Mountains," one of the specific names applied to it being 

 alpestris. It is, therefore, a mountain genus, which once lived in 

 the Rocky Mountains, and may even have survived there until des- 

 troyed by the cold of the glacial epoch. 



If the above arguments are justified, it is easy to understand why 

 so many of the Florissant plants, notwithstanding their antiquity, 



"For a general discussion of this matter, see A. R. Wallace's Island Life. 



