144 IMESOZOIC FLORAS OF INITED STATES. 



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

 go further and take it as good proof that the l)eds are not older tliaii 

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

 the Yorkshire and the Siberian strata may he 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, l)esides PterophyUum rajmahalence, 

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

 Lower Oolite. They are Ptcrojiln/lluin aciudic and Xil.sonia /ifeni/iln/l- 

 loides. Both of these are given ))y Xathorst as found in the Rhetic of 

 Scandinavia. The latter has not hitherto l)een found in strata younger 

 than the Rhetic. Pterophlyllum (vqnalc has been noted In* Schenk as 

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

 he thinks, of Lower Oolite age.'^' 



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

 the Yorkshu-e 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. ZeiUer, in his paper discussing the age of the 

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

 ta page 478, ' states that it is questionable whether tlie 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 stud}'. 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. 



fcOp. cit., p. 26.5. 



<• Remarque.s sur la (lore fossilp de I'Altai a piopos ties dcrnirres drcouveites pult'ohotaniques de MM. 

 Bodenbender et Kurtz dans la R^publique Argentine, par. M. R. iieiller: Bull. Soc. Cieol. de France, 3" s^r.. 

 Vol. XXI\', Paris, 1896, pp. 466-487. 



