300 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. LFol. VL 



Aix, in Provence, considered as eocene. But now, after a more careful 

 revision, drawn from more extended sources, he writes that while, by 

 the presence of many genera, "there is an evident relation of the Floris- 

 sant flora with that of the European miocene, yet by the affinities and 

 even identity of some of the species with those of the flora of the gyp- 

 sum of Aix, which, according to Saporta, includes types related to those 

 of the whole extent of the tertiaries from the upper cretaceous to the 

 oligocene and above, I should rather refer this group to the lower mio- 

 cene or oligocene." 



Both Lesquereux and Cope agree in placing the Florissant beds at the 

 ^ame horizon as those of Elko, Nev., and also those directly below the 

 Fish-cut beds at Green Eiver, Wyoming. Lesquereux has identical 

 species also from White river, Colo., among specimens communicated by 

 Mr. Denton. Cope calls the Florissant and Elko deposits the Amyzon 

 beds, from the prevalence of that type of fish, and refers them to the 

 " later eocene or early miocene." 



Mr. Clarence King i^laces the Green Eiver deposits in the middle 

 eocene, but considers the Elko deposits of the same age. 



We may therefore provisionally conclude, from the evidence aflbrded 

 by the plants and vertebrates, that the Florissant beds belong in or near 

 the oligocene. 



At i)resent no geological conclusions can be drawn from what is known 

 of the insects. So far as specific and generic determination has pro- 

 ceeded, nothing identical has been found in the Green Eiver and Floris- 

 sant beds, but some remarkable aflinities have been noticed. To attempt, 

 however, to draw any conclusion as to the age of either of these deposits, 

 and especially of that of Florissant, before a closer examination is made, 

 would be folly. The entire series of fossil insects from the beds of Aix, 

 Oeningen, and Eadoboj requires a careful generic revision, the Coleop- 

 tera alone, perhai)s, excepted, and until this is done it will be difficult, 

 to make much use of the information given us in the works of European 

 authors. This should not be considered as reflecting upon the character 

 of these works, for it must be remembered that they weie nearly all 

 completed thirty years ago and could not be expected to meet present 

 demands. It is, indeed, not impossible that the richer American fields, 

 the exploitation of which has only just begun, may yet be found the best 

 basis for the study of tlie relationship of the tertiary insect faunas of 

 Europe. 



