54 F. 11. Knouiltoti — Jurassic Flora of Oregon. 



has been held by the writer For some years ; in fact all original 

 as well as subsequent collections have tended to prove it, as 

 they have also the distinctness ot the Jurassic and Cretaceous 

 floras of the region. I have, however, ventured to submit the 

 question to Prof. A. G. Nathorst of Stockholm, who is per- 

 haps the greatest living authority on the Jurassic floras of the 

 world. His comment is as follows : " As to the ' Jurassic 

 flora ' of Douglas County, Oregon, I can but think that the 

 American paleobotanists are right in regarding it as a true 

 Jurassic flora. For even if some of the specific determina- 

 tions are incorrect, this has no influence on the question of 

 age. If, therefoj-e, the saine flora is found in California, it is 

 naturally also of Jurassic age. In this matter I do not think 

 it possible that there can be more than one opinion prevaildng 

 among paleobotanists." 



A Comparison of the Jurassic and Lower Cretaceous 

 Floras of tbe Oregon— California Areas. 



If these two floras comprised a small number of species 

 each, it could be argued tliat lack of identical forms might be 

 corrected by more extensive collections, but fortunately both 

 floras are relativel}^ large, the Jurassic embracing lUO and the 

 Lower Ci'etaceous 59 forms. Most of the localities have been 

 extensively — even exhaustively — exploited, and the numbers 

 are sutficiently large to bring out the interrelationship if such 

 existed. An examination of the two lists, however, shows 

 that there is only a single species {Sequoia Reichenhachi) 

 common to the two, and as this species is of very wide verti- 

 cal range, it would seem to be settled conclusively that there 

 is no real relationship between the Jurassic and Lower Creta- 

 ceous floras. This conclusion is made more positive and 

 significant by the fact that in certain localities, as near Rid- 

 dles, they occur practically in the same section. That they 

 may yet be found commingled in the same beds is a contin- 

 gency that seems highly improbable, though that the Jurassic 

 flora may sometime be found in the lower part of the Knox- 

 ville of the Sacramento Valley, below the Lower Cretaceous 

 flora and fauna, is quite possible. 



It is not within the scope of the present paper to enter into 

 an exhaustive discussion of the Lower Cretaceous flora of Cali- 

 fornia and Oregon beyond the general statement of its obvi- 

 ous alBnities. To some extent this has already been done by 

 Professor Fontaine." 



Evidence of the Invertebrates. 



As stated in the opening paragraphs of this paper, it is not 

 the intention to enter into a critical analysis of the inverte- 

 * U. S. Geol. Surr., Mon. 48, pp. 270-273, 1905. 



