156 



LARAMIE FLORA OF THE DENVER BASIN. 



Laramie. It rather closely resembles Rham- 

 nus? williardi Knowlton, 47 from the Fox Hills 

 sandstone of the Greeley quadrangle, Colo. 

 That species is a little smaller and not quite 

 so truncate at the base, but in nervation there 

 appears comparatively little difference. The 

 type specimen of R. belmontensis, however, 

 which is preserved in the United States 

 National Museum (No. 10958), presents an 

 entirely different aspect, The nervation is 

 very thin and delicate, and the nervilles are 

 made out with much difficulty. Notwith- 

 standing the agreement between the leaves in 

 outline, disposition of nervation, etc., it is 

 impossible to believe that the two could belong 

 to the same species. 



Occurrence: Laramie formation, Marshall 

 (formerly Belmont), Colo. 



Rhamnus brittoni Knowlton, n. sp. 



Plate XV, figure 6; Plate XXIV, figure 8. 



Rhamnus brittoni Knowlton [nomen nudum], U. S. Geol. 

 Survey Bull. 696, p. 544, 1919. 



Leaves rather stiff and evidently coriaceous, 

 lanceolate, 8 or 10 centimeters long, 3 or 4 

 centimeters wide, apparently obtusely wedge- 

 shaped at the base, long-pointed and sharply 

 acuminate at the apex, broadest about one- 

 third the length of the blade above the base; 

 margin entire; midrib moderately strong, per- 

 fectly straight; secondaries relatively strong, 

 numerous (about 14 pairs), close, parallel, at 

 an angle of about 50°, very little curved up- 

 ward, ending in the margin; nervilles very 

 numerous, close, parallel, mainly unbroken, 

 oblique to the secondaries. 



The nearest relative of this species appears 

 to be Rhamnus elegans • Newberry 48 (now 

 R. belmontensis) , from the Laramie at Belmont, 

 now Marshall, Colo., with which* it agrees 

 closely in size and shape but differs in the more 

 numerous close, parallel secondaries, which 

 are but little curved upward. The nervilles 

 are much the same in both. 



This species is also related to Rhamnus 

 salicif alius Lesquereux 49 but is much broader 

 and has more numerous secondaries, which are 

 at a lower angle of divergence with the midrib ; 

 the nervilles are about the same in both. 



« Knowlton, F. H., The flora of the Fox Hills sandstone: U. S. Geol. 

 Survey Prof. Paper 98, p. 91, pi. 16, figs. 1, 2, pi. 17, figs. 1-4, 1916. 



« Newberry, J. S., U. S,. Geol. Survey Mon. 35, p. 117, pi. 50, fig. 2, 1898. 



*> Lesquereux, Leo, The Tertiary flora: U. S. Geol. Survey Terr. Rept., 

 vol. 7, p. 282, pi. 53, figs. 9, 10, 1878. 



Occurrence: Laramie formation, Erie, Colo., 

 collected by N. L. Britton, in whose honor the 

 species is named. 



Rhamnus? pealei Knowlton, n. sp. 



Plate XV, figure 7. 



Rhamnus? pealei Knowlton [nomen nudum], U. S. Geol. 

 Survey Bull. 696, p. 548, 1919. 



Leaf evidently rather thick, ovate-elliptical, 

 unequal sided, base truncate on one side, 

 wedge-shaped on the other, apex obtusely 

 acuminate; margin apparently entire; midrib 

 relatively very thick; secondaries 10 or 12 

 pairs, alternate, strong, Jiearly at right angles 

 near the base on one side, others gradually at a 

 more acute angle, camptodrome; nervilles 

 numerous and prominent, mainly broken and 

 oblique to the secondaries. 



In the specimen figured nearly all of the 

 margin is lacking, but so far as can be made out 

 it was perfectly entire. This leaf is 7 centi- 

 meters long and a little over 3 centimeters 

 broad; it is very regular in size from the un- 

 equal-sided base to about the upper fourth of 

 its length, where it narrows to the rather 

 obtusely pointed apex. 



Occurrence: Laramie formation, cut on 

 Moffat railroad (Denver & Salt Lake) about 

 6 or 8 miles north of Golden, Colo., collected by 

 A. C. Peale, for whom it is named. 



Rhamnus sp. 



Plate XVII, figure 1. 



In the material from Popes Bluffs, near 

 Pikeview, Colo., was found the single fragmen- 

 tary leaf here figured. It was apparently 

 about 4 centimeters long and 2 centimeters 

 wide, with entire margin and a rather abruptly 

 rounded and obtuse apex; the base is destroyed. 

 It has a very thick midrib and at least 10 pairs 

 of light camptodrome secondaries. The most 

 marked feature of this little leaf consists of the 

 nervilles, which are very numerous, mainly 

 forked or broken, and oblique to the second- 

 aries. 



This leaf is at once suggestive of either 

 Rhamnus cleburni Lesquereux or Rhamnus 

 goldianus Lesquereux, both well-known Den- 

 ver species, but it is smaller than either, though 

 approaching R. goldianus most closely. In the 

 nervation, except for size, it is not different 

 from either of these species. 



