THE FOSSIL PLANTS OF THE PAYETTE FORMATION. 



By F. H. KNOWLTON. 



The following report is based on a collection of fossil plants obtained 

 during the past season by Mr. Waldemar Lindgren from the lake beds 

 of the Snake River, in western Idaho, to which the name Payette for- 

 mation has been given. The matrix in which the plants are preserved 

 is in general a fine-grained clay, which has retained their outline and 

 nervation with remarkable fidelity. 



Following is a list of localities from which the plants were obtained : 



1. Two miles southeast of Marsh post-office, Boise County, Idaho. 

 From a coal prospect. 



2. One mile southeast of Marsh post-office, Boise County, Idaho. 

 From a canyon on the road to Willow Creek and several hundred 

 feet above the Payette River. 



3. Robb's coal prospect, 1 mile south of Horseshoe Bend post-office, 

 Boise County, Idaho. 



4. Cartwright's ranch, on Shafer Creek, 4 miles southeast of Horse- 

 shoe Bend post-office, Boise County, Idaho. 



5. Near Idaho City, Boitee County, Idaho. 



SYSTEMATIC ENUMERATION OF SPECIES. 



DRYOPTERIS IDAHOENSIS n. sp. 

 PL XCIX, figs. 1, 2. 



Outline of frond unknown; frond twice pinnate, pinnse approxi- 

 mate, subopposite, deeply pinnate, the segments oblong, obtusely 

 acuminate, or upper pinnse lobed at base, the remainder entire or 

 undulate; secondary rachis strong, curved upward; each segment 

 with a strong midvein giving off forked veins. 



As may be seen from the figure, this species is represented only by 

 a fragment, which, were it not for the fact that it is so distinctly 

 unlike any previously described American form, would be almost too 

 fragmentary for notice. The original form of the frond can not be 

 determined. The specimen consists of a portion of the rachis with 

 parts of four pinnse, only two of which are approximately perfect. 

 The pinnae are close together, subopposite in attachment, and slightly 

 18 GEOL, PT 3 46 ? 21 



