38 F. H. Kno'iolton — Jurassic Flora of Oregon. 



Doctor Stanton makes the following comment on this fauna : 

 "The collection consists of a number of small lots containing 

 very few specimens, the most abundant and persistent being 

 Aucella crassicollis Keyserling, which past experience shows 

 to be characteristic of the upper part of the Knoxville forma- 

 tion and is believed to be confined to the Lower Cretaceous. 

 In several of the lots there are a few ammonites and other 

 fossils that are also Knoxville forms." 



The significance of this association of flora and fauna will be 

 considered latei'. 



5. Big Bar, Trinity County, California. 



This area, which covers less than two square miles, is on the 

 Trinity River, about twenty miles west of Weaverville, ,Cali- 

 fornia, and is not less than 150 miles from the areas already 

 considered in Oregon. The entire section of Jurassic rocks in 

 this vicinity does not exceed 200 feet in thickness, and lies on 

 the sharply upturned edges of older, probably Paleozoic strata, 

 and is itself inclined from 20 to 45°. It is composed of soft 

 "gray shales and sandstones, with a small proportion of tine 

 conglomerate," and apparently belongs to the lower part of the 

 Knoxville. 



Fossil plants are abundant in this locality, and are scattered 

 irregularly throughout the section, though most numerously "in 

 the lower portion. They embrace 20 well-marked species 

 [see table on pp. 43-45] and as stated in the original report, thej 

 "prove beyond question that the beds containing them are 

 similar in age to the Jurassic of Oregon, since all but three of 

 the forms {Onycoldopsis [fruit], Hausmannia, and Pagio- 

 phyllum falcatum) are common to the two areas." 



In the same bed with the plants a few shells have been 

 found. Only one of these has been positively determined as 

 Aucella crassicollis, the others being unidentified forms of 

 Pecten, Mytilns, Cyjorina, and TInio, the latter proving that 

 there were alternations of fresh-water and salt-water conditions. 

 These fossils, says Doctor Stanton, "are certainly upper 

 Knoxville and hence Lower Cretaceous, as shown by the 

 presence of typical specimens of Aucella crassicollis.^'' 



6. Rattlesnake Creek, Trinity County, California. 



Twenty-five miles south of Big Bar there is another small 

 area of Jurassic plant-bearing beds lying in the drainage of 

 Rattlesnake Creek, 7-J miles southwest of Peanut, Trinity 

 County, California. As at Big Bar, the plant beds reston the 

 upturned edges of older rocks. 



Only three species of plants have been found at this local- 

 ity : Cyclopitys oregonensis Font., Tceniopteris vittata Brongn., 



