DISTRIBUTION OF THE FLORA 397 



creek in the Roseburg quadrangle. In the Riddles area the following 

 eight forms have been reported by Ward and Fontaine : 



Sagcnopteris niantclU ? Scbenk. 

 Sagenoptciis orcyonensis ITontaiDe. 

 Sagenoptcris nervosa Fontaine. 

 Angiopteridiuia strictiiwrvc latifoliam Fontaine. 

 Dionites huchianiis ahietimis Ward. 

 Nageiopsis latifolia Fontaine. 

 Populiis 1 r/cer Fontaine. 

 Sapindopsis oregoncusis Fontaine. 



In this Riddles area of the "Myrtle formation" fossil plants are rare, 

 but shells are qnite abundant. The fauna, it is true, does not contain a 

 large number of species, but they are characteristic, and the fauna and 

 flora agree with the stratigraphy in correlating this area of the "jMyrtle" 

 with the Shasta on the Western side of the Sacramento valley. The Rid- 

 dles area, including the mass on Iron Mountain creek, is the only one in 

 Oregon that has .yet yielded the Shasta ilora. 



Distribution or the Jurassic Flora in the "Myrtle Formation" 



OF Oregon 



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 the 

 "Myrtle formation." Southeast of it lies the Riddle region and Iron 

 Mountain creek, where the "Myrtle formation" 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 "Ju- 

 rassic flora of Oregon." At one point the line of deformation is over- 

 lapped by the Jurassic flora, where it reaches Cow creek at Nichols sta- 

 tion." 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 faiina on the northwest 

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



The most impressive fact in the field, knowing the distribution of the 

 fossils, is the occurrence of only one form of Aucella witTi the Jurassic 

 flora of Oregon. The flora probably extends far down in the portion of 

 the "Myrtle formation" characterized by Aucella piochi, Init no such 



'^Attention should be recalled to the .Tnrassic plant founrl in the Kiddles area fseo p. 

 ."iT^) and the one found in the Dothan (see p. .370). The last is the only one yet found 

 in Oregon below the horizon of Aucella crdssicollis and Aucella inochi. 



