46 F. H. Knowlton — Jurassic Flora of Oregon. 



of the tioras of the several areas. Thus, of the 27 species 

 coniposiiio; the Oroville flora, 12 species occur also in the 

 Douglas Count}' areas. Of the Qi^ forms found on Thompson 

 Creek, 32 are common to the localities near Nichols Station, 

 and of the 20 forms occurring at Elk liiver, in Curry County, 

 all hut one are common to Douglas County. The close relation 

 between the Oregon areas and that at Big Bar, California, is 

 shown by the fact that all but 3 of its 19 forms are common 

 to the former, and of the 3 species reported from Rattlesnake 

 Creek, 2 are common to the Oregon localities and one to Big 

 Bar. This proves beyond all reasonable doubt that the plant 

 beds of the several localities are identical in age. Whatever 

 is decided regarding any one of them must apply with equal 

 force to all. ' 



We may now proceed to an analysis of the flora to ascertain 

 its bearing on the age of the strata. Of the 100 forms com- 

 posing the flora 15 are not specifically named and 47 are found 

 in outside areas, mainly beyond the limits of North America, 

 thus leaving 38 species, or considerably less than fifty per cent., 

 as endemic. Of these forms that are peculiar, Professor Fon- 

 taine* has well said that " none are incompatible with the con- 

 clusion that the age of the strata is Jurassic. On the contrary, 

 so far as they throw any light on the question of age, they indi- 

 cate that it is Jurassic."t 



The value of species new to science and those whose deter- 

 mination is questioned, in attempting to fix the age of the beds 

 contahiing them lies in their affinities, or close relationship, 

 with species whose position is known. It may be worth while 

 in the present connection to review a number of the peculiar 

 species of this flora to ascertain their relationships. Cladophle- 

 his vaccensis is very close to, and indeed was at first identified 

 with, Asplennom whithiense ienue Heer, from the Jurassic of 

 Siberia. CladophleMs pecopteroides is thought by Professor 

 Fontaine to be the Oregon representative of Pecopteris, ohtusi- 

 folia, a species of the Yorkshire beds. Scleropteris oregonen- 

 sis is close to S. Pomelii Zigno of the Italian Oolite. Taeniop- 

 teris ? oregonensis may be a small, narrow leaf of T. vittata^ 

 though it has some resemblance to Cycadites sibericus Heer, 

 of the Jurassic of Siberia, which is a Taeniopteris rather than a 



*U. S. Geol. Surv., Mon. 48, p. 141. 



\ Mr. Diller has given a portion of this quotation [" so far as they throw- 

 any light on the question of age, they indicate that it is Jurassic "] as a full 

 expression of Professor Fontaine's opinion regarding the bearing of the 

 Oregon plants on the question of age. As shown above, this quotation 

 applies only to the new and not specifically named species, while Fontaine's 

 opinions regarding the significance of the positively determined species occur 

 on the two or three succeeding pages of his paper [U. S. Geol. Surv., Mon. 

 48, pp. 141-145]. 



