FLORA OF TJJK OJtEKN lil\ KU OKOUP. I95 



the following species. Tlie secondary veins are close, parallel, with inter- 

 mediate shorter tertiary veins of the same character as in It. I/illice. 



Ilab.—Florisssini. U. S. Gcol. Expl. Dr. F. V. Hayden. 



The specimen described in Suppl. to "Annual Report," 1871, is from 

 Green River. 



Khus subrhoniboidalis, sp. nov. 

 Plate XLI, Figs. lG-19. 



Leaflets membranaceous, ovate or sub-ihomboidal, lomided to a short petiole, 

 deeply dentate, acuminate; lateral nerves curved, craspedodrome. 



Though these three leaflets are so much alike in their forms that it 

 is not possible to refer them to two species, their nervation is very differ- 

 ent on account of the position of the large teeth, one or two on each side. 

 In tig. 10 the teeth are in the upper part of the leaflet and the lateral veins 

 curve upward to reach them, and are distant from the upper more open 

 parallel ones; in the other leaflets, figs. 17 and 18, the two pairs of teeth 

 being lower, the lateral nerves are merely curved in their direction toward 

 them and parallel from the base. It is not possible to decide whether 

 these leaflets pertain to pinnate or to trifoliate leaves, like those of the 

 common and so very variable R. aromatica. Their relation to those 

 described by Saporta as R. rhomhoidalis, "Et.," iii, 111, p. 206, pi. xvi, 

 figs. 2, 3, is remarkably close. 



ifo*.— Florissant. U. S. Geol. Expl. Dr. F. V. Hayden, and also in the 

 Collection of the Princeton Museum, Nos. 751 and 832. 



Rhus V e X a n s , sp. nov. 



Plate XLI, Kig. 20. 



Leaves trifoliate, loug-petioled ; leaflets cuneiform, enlai'ged, obtusely denttite or 

 lobate in the upper part aud there abruptly narrowed to an obtuse apex ; nervation 

 mixed. 



This small leaf is so exactly similar to a variety of R. aromatica {R. 



frilobafa, Nutt.), especially found living in Texas, that it is scarcely possible 



to find any point of difference. In the living species the terminal upper 



lobes of the pinnules are more distinctly dentate, but its smaller leaves, of 



the same size as the one figured, have exactly the same subdivisions. The 



nervation is also the same, the lower lateral veins being camptodronie, the 



