390 J. S. DILLER THE JURASSIC FLORA OF OREGON 



ner Mine area. The bulk of the evidence supports the view that the 

 deposition of the plant l)eds at Oroville occurred during a quiet interval 

 in the time of volcanic activity, but it is not yet certain that they are not 

 later and occupy a syncline folded into the underlying volcanics. 



FOSSILS AXD AGE 



A full account of the flora in the Monte de Oro formation is given by 

 Professors Ward and Fontaine in the Twentieth Annual Eeport of the 

 U. S. Geological Survey, part ii. The flora contains 28 distinct forms, 

 of which 14 are new. There are 12 forms that may be compared with 

 previously known ones in fixing the age, and 7 of these are Jurassic. 

 The conclusion reached by the paleobotanists is that "the comparison of 

 the Oroville plants with knoAvn floras shows that most of the forms for 

 which any relationship with known plants can be made out find their like 

 in the Lias and Oolite, or, without distinguishing these, in the Jurassic." 



The shells found in the Monte de Oro formation by Mr Storrs have 

 been examined by Doctor Stanton, who states that — ■ 



"The fossils from the plaut-bearing Mesozoic beds near Oroville, California, 

 are especially interesting for the reason that this locality has not previously 

 yielded any invertebrates. Unfortunately the collection does not contain any- 

 thing specifically identifiable with fossils from any well-known horizon on the 

 we.st coast. The most abundant form is an aviculoid shell that I doubtfully 

 referred to Eumicrotis. With these there are specimens of Pinna, Trigonia, 

 and Belemnites. The whole assemblage has a decided Jurassic aspect, and, iu 

 my opinion, the formation yielding them is older than the aucella-bearing 

 Mariposa formation." 



In September, 1907, I again visited the Oroville locality with Mr 

 Storrs and made additional collections in the hope of finding something 

 distinctive. These were referred to Doctor Stanton, who reports as fol- 

 lows: 



"About a year ago, in reporting on another collection obtained by Mr Storrs 

 from these beds, I expressed the opinion that they are Jurassic and older than 

 the Mariposa beds. The fossils now under examination add several species to 

 the previous list, although I am still unable to assign them to described spe- 

 cies, and they do not therefore afford a good basis for correlation with well 

 established horizons. Perhaps the most important addition is the form doubt- 

 fully referred to Aucella. It is represented by one fairly good valve and a 

 fragment of another, which might belong to either A. piochi of the Kuoxville 

 or to A. errinfftoni of the Mariposa, as far as can be determined from the feat- 

 ures preserved. Unfortunately there is no right valve in the collection and 

 the generic reference is not positive. If it is really an Aucella, the age of the 

 beds is either JIariposa or Knoxville — more probably the former. The general 



