144 MESOZOIC FLORAS OF UNITED STATES. 



that the Oregon strata are of the same age as those of Siberia. We may 

 go further and take it as good proof that the beds are not older than 

 Lower Oohte. This large element of the Oregon flora common to both 

 the Yorkshire and the Siberian strata may be taken as strong confirma- 

 tion of Heer's belief in the identity of the age of the two formations. 



There are in the Oregon flora, besides Pterophyllum rajmahalence, 

 two previously known plants that point to a somewhat older age than 

 Lower Oohte. They are Pterophyllum (equals and Nilsonia pterophyl- 

 loicles. JBoth of these are given by Nathorst as found in the Rhetic of 

 Scandinavia. The latter has not hitherto been found in strata younger 

 than the Rhetic. Pterophlyllum cequale has been noted by Schenk as 

 found in the beds of the Tumulu coal field of China. " These strata are, 

 he thinks, of Lower Oolite age.'' 



There can be no doubt, in the opinion of the present writer, that 

 the Yorkshire Lower Oolites, the strata of eastern Siberia and of the 

 Amoor, made known by Heer, and the Oregon beds are of the same 

 age. The only question is, What is that age? The investigations of 

 the English geologists would seem to have settled the question for the 

 Yorkshire formation. Zeiller, in his paper discussing the age of the 

 fossil flora of the Altai made known by Schmalhausen, in a footnote 

 to page 478,' states that it is questionable whether the Siberian and 

 Amoor plants described by Heer are really Lower Oolite in age. He 

 thinks that the resemblance of this flora, in a number of its elements, 

 to that of the Rhetic of Scandinavia makes the question an open one 

 and that the age may be Lower Lias or even Rhetic. He takes pains, 

 however, to state that he does not maintain that Heer's conclusions 

 are erroneous, but that the question of age in the case of these strata 

 merits further study. The key to the whole matter is the correctness 

 of the determination of the age of the Yorkshire beds. So far as my 

 knowledge goes no one has questioned the correctness of the conclu- 

 sions of the English geologists regarding the age of the Yorkshire strata. 

 That being established as Lower Oolite would certainly indicate a simi- 



« Schenk, Jurassic Plants of China, pp. 247-248, pi xlviii, fig. 7. 



6 0p. cit., p. 265. 



f Remarques sur la flore fossile de I'Altai a propos des dernieres decouvertes paleobotaniques de MSI. 

 Bodenbender et Kurtz dans la Republique Argentine, par. M. R. Zeiller: Bull. Soc.GeoI.de France, 3° ser.. 

 Vol. XXIV, Paris, 1896, pp. 466-487. 



