F. H. Knowlton — Jurassic Flora of Oregon. 39 



and Sequoia Heichenbachi (Gein.) Heer. The latter species is 

 a form of such wide vertical range that it is of little value in 

 fixing the age of beds in which it may occur, hence its inferen- 

 tial use to prove the beds on Rattlesnake Creek to be of 

 extreme upper Knoxville or lower Horsetown age, where this 

 species has also been found, is not warranted. 



Many shells are stated to be present in the same strata with 

 the plants, concerning which Doctor Stanton reports as fol- 

 lows : "Among the fossil plants are two small shells which 

 appear to be young specimens of U^iio, though they may 

 belong to some marine genus instead." 



7. Oroville, Butte County, California. 



At this locality Jurassic rocks form an area about 2 miles in 

 length and 2/5 of a mile in width, on the southern slope of 

 Monte de Oro, about 3 miles northeast of Oroville, Butte 

 County, California. These rocks, to which the local name of 

 the Monte de Oro formation has been given, are composed of 

 "slates, sandstones, and conglomerates in small layers, irreg- 

 ularly interbedded " ; they are much disturbed and the true 

 thickness cannot be made out, though thought to be some- 

 where between 450 and 900 feet. 



This area has afforded a rich floi-a, and was the first to be 

 described of any considered in this paper ; it contains 

 27 species [see table on pp. 43-45]. They are typically 

 Jurassic, and as nearly half were subsequently found to be 

 common to the Douglas County region they are of much 

 importance in settling the Jurassic age of the plant beds in the 

 latter area. Unfortunately the invertebrate collections are Tiot 

 large from the plant beds at Oroville, and comprise new or 

 undeterminable species of the genera Ostrea., Pecteii, Aucella f, 

 Modiola, Trigonia, Cardiuvi f and Belemnites. Regarding 

 the age as indicated by the Aucella % Doctor Stanton says : "If 

 it is really an Aucella the age is either Mariposa or Knoxville, 

 more probably the former. The general character of the other 

 forms is suggestive of the older Jurassic faunas of theTaylors- 

 ville region, but it must be admitted that there is no definite 

 evidence of this." 



Stratigkapbic Relations of the Beds Containing the Lower 

 Cretaceous Flora op Oregon and California. 



1. Near Riddles, Douglas County, Oregon. 



In the vicinity of Riddles, Oregon, and including a small 

 area on Iron Mountain Creek, there is a mass of rocks that has 

 been pretty definitely connected with the upper portion of the 

 Myrtle formation, since it is directly on the strike with that 



