KNOWLTON.] PLANTS OF THE PAYETTE FORMATION. 733 



ACER TRILOBATUM PRODUCTUM ? Heer. 

 PL CII, fig. 3. 



The collection contains only the single specimen figured of this 

 form. It is unfortunately broken at the apex, so that its reference to 

 this variety of Acer trilobatum is more or less uncertain. From the 

 configuration of the part preserved there is, however, little doubt as 

 to its correctness. 



Locality : Two miles southeast of Marsh post-office, Boise County* 

 Idaho. 



RHUS PAYETTENSIS n. sp. 



PI. CI, figs. 6, 7. 



Leaflet coriaceous, ovate in outline, abruptly rounded or truncate 

 at base, and slightly unequal-sided, obtuse (?) at apex; margin nearly 

 entire on one side, remotely toothed on the other, the teeth small, 

 sharp, pointing upward; midrib thin, somewhat irregular; seconda- 

 ries about 6 or 7 pairs, opposite or subopposite, emerging at an angle 

 of 35, much curved upward, and ending in or sending weak branches 

 to the few marginal teeth; nervilles strong, mainly percurrent; finer 

 nervation quadrangular. 



The smallest leaflet is 5.25 cm in length as now preserved, and was 

 probably not far from 6 cm in length when perfect. It is just 3 cm in 

 width. The whole base is unfortunately not preserved^ but from the 

 configuration it appears that it was slightly unequal-sided. 



This species is referred to the genus Rhus on the strength of its 

 resemblance to the living Rhus toxicodendron, the common poison ivy. 

 This small leaflet resembles certain small forms of this species in 

 quite a marked degree. The living form has usually more strongly-cut 

 leaflets, but in general outline and nervation they are quite similar. 



This species does not appear to be particularly close to any of the 

 numerous fossil species that have been described from similar beds. 



Locality: Two miles southeast of Marsh post-office, Boise County, 

 Idaho. 



TRAPA AMERICANA n. sp. 

 PL CII, fig. 7a. 



Fruit two-horned, the horns long, slender, acuminate, pointing 

 upward at an angle of about 45 ; central prominence between the 

 horns obtuse, prominently striate ; body of fruit thick, wedge-shaped 

 below. 



This fruit belongs to the two-horned Asiatic type of the genus. It 

 is obverse-deltoid or broadly wedge-shaped in outline. The distance 

 from base to extremity of horn is just 2 cm , while the distance between 



