No. 517] 



33 



much so that one is in some difficulty to point out any 

 tangible differences. This is equally true of a number 

 of other cases, of which the following are illustrative: 



Florissant. 

 Finns wheeleri Ckll. 

 Finns sturgisi Ckll. 

 Ailanthus americana Ckll. 

 Sambucus newtoni Ckll. 

 Anona spoUata Ckll. 



Populus lesquereuxi Ckll. 

 Quercus lyratiformis Ckll. 

 Sapindus coloradensis Ckll. 



Living. 

 Finns flexilis James. 

 Pinus tceda L. 

 Ailanthus glandulosa L. 

 Sambucus arboreseens Nutt. 

 Anona glabra L. 



yndi H. & A. 



So numerous are the resemblances to the living flora 

 that one might well feci persuaded to refer the beds to 

 the Pliocene— certainly better there than to the Oligocene 

 or Eocene! However, the Florissant fishes, with the 

 exception of Amia, are of extinct genera, and no less 

 than 178 genera of insects are supposed to be extinct. 

 For a variety of reasons, based chiefly upon a study of 

 the insects, I believe that the Florissant period corre- 

 sponds with Osborn's "Fifth Fauna] Phase" (Bull. 361, 

 V. S. Geol. Survey ), in which a new fauna was invading 

 the country from Furasia, while connection with South 

 America had not yet been established. Some of the 

 Florissant groups of insects, such as the Aphidida? and 

 Bombyliida3, seem to represent the original American 

 fauna' uncontaminated ; while others show old world 

 types, the most significant and interesting of which is 

 the tsetse fly (Glossina)? Osborn's "Fifth Phase" in- 

 cludes the Middle and Upper Miocene, and so far as may 

 be judged, Florissant should belong near the middle 

 of it. 



The attempt to correlate the Florissant beds with other 

 American floras ascribed to the Miocene brought out a 

 number of difficulties. With the exception of the little- 



