PROCEEDIN-GS OP THE NATIOITAL MUSEUM 



VOL. 72 



Typha lesquereuxi, Cockerell 



Salix inquirenda Knowlton, (?)_. 



Salix knowltoni Berry 



Quercus simulata truncata Berry. 

 Sapindus lancijolius Lesquereux. 

 Trapa americana Knowlton 



Florissant, 

 Colo. 



X 



X 



Mascall, 

 Oreg. 



X 



Latah, 

 Wash. 



(?) 



X 



(?) 



Payette, 

 Idaho 



X 

 X 



X 



The exact age of Florissant, the Mascall, Latah, and Payette for- 

 mations has been the source of considerable differences of opinion in 

 the past. Both the Florissant and Mascall beds are now generally 

 considered to be middle Miocene, although Knowlton's latest unpub- 

 lished opinion was that the Florissant flora was upper Miocene, and 

 I think the evidence for this is reasonably conclusive. The Latah 

 and Payette floras are similarly considered Miocene, although agree- 

 ment has not been reached as to just what part of the Miocene they 

 represent. After studying large recent collections from the Latah 

 formation I have concluded that it is not older than middle Miocene 

 and probably younger, so that the Esmeralda flora seems to me to 

 show conclusively that it is not older than middle Miocene and is 

 almost certainly upper Miocene. This conclusion from the plant 

 evidence coincides with J. W. Gidley's age determination of the 

 Esmeralda vertebrates. 



Phylum PTERIDOPHYTA 



Order HYDROPTERALES 



Family SALVINIACEAE 



Genus AZOLLA Lamarck 



AZOLLA TERTIARIA, new species 



Plate 1, figs. 9, 10 



The basis of this species is a considerable number of whole plants 

 and scattered plant fragments at certain horizons in the clay where 

 they are preserved as impressions. The plant body in the best- 

 preserved examples is about a centimeter in diameter and consists 

 of a flat branched stem covered with tiny oval leaves somewhat 

 variable in shape, slightly under a millimeter in length, generally 

 crowded and imbricated, becoming densely so around the periphery 

 where they are more rounded and distinctly concavo-convex. 



