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



of the type locality for the Myrtle on Mj'rtle Creek in the 

 Roseburi;- qniKlranii-Je. Tliese beds contain a small bnt very 

 important liora of 8 species, as follows : 



Sagenopteris 3iantelli? Schenk 

 Sagenopteris oregonensis P'oiit. 

 Sagenopteris nervosa Font. 

 Angiopteridiuni strictinerve latifoUuni Font. 

 Dioonites Biichianus abietinus Ward. 

 Nageiopsis latifolla Font. 

 Popuhcs ? Rlcei Font. 

 Sap)indopsis oregonensis Font. 



This flora is identified without hesitation as beino; of Lower 

 Cretaceous age, or Neocomian. The presence of the species 

 of dicotyledons shows conclusively that it is younger than 

 the "Jurassic flora of Oregon," a fact also proved by the 

 stratigraphic relations and invertebrate fauna. The latter, 

 although stated to be abundant, is not listed by Mr. Diller, 

 though held to be characteristic and proving the correlation 

 between these beds and those containing a similar fauna on 

 the western side of the Sacramento Valley. 



The stratigraphic relations between the beds near Riddles 

 which contain the Lower Cretaceous flora, and those to the 

 northwest containing the Jurassic flora, is well set forth by Mr. 

 Diller* in the following statement: "A line of deformation 

 runs northeast and southwest through the region of Nickel 

 Mountain and Dodson Butte. It follows a prominent ridge 

 and appears to mark approximately the limit between the two 

 floras of ' Myrtle formation.' Southeast of it lies the Riddles 

 region and Iron Moimtain Creek, where the " Myrtle forma- 

 tion " contains the 'Shasta flora,' while to the northwest of 

 it lie the larger irregular areas of the ' Myrtle,' containing 

 locally on Thompson Creek and Elk River the 'Jurassic flora 

 of Oregon.' At one point the line of deformation is over- 

 lapped by the Jurassic flora, where it reaches Cow Creek at 

 Nichols Station. In general, on account of the overlapping 

 ' Myrtle formation,' it may be claimed that the ' Myrtle ' 

 containing the Jurassic flora lying northwest of that containing 

 the Shasta flora must be older. So it seems also from the 

 entire absence of any Horsetown fauna on the northwest side 

 of the axis in the same series near the Jurassic flora." 



From this exposition it appears very clear that the Myrtle 

 formation may be divisible, at least paleontologically, into two 

 parts, the upper of which is characterized by the presence of a 

 Lower Cretaceous flora and fauna, while the lower is equally 

 marked by the presence of a Jurassic flora. The two floras 



*0p. cit., p. 397. 



