166 



LARAMIE FLORA OF THE DENVER BASIN. 



exceedingly strong below, becoming very thin 

 above; secondaries about 12 pairs, alternate, 

 thin, arising at a low angle, much curved up- 

 ward, camptodrome, arching near the margin, 

 along which they pass in a series of loops; 

 nervilles numerous, both percurrent and broken; 

 finer nervation forming an intricate network of 

 large and small irregularly quadrangular 

 areolae. 



This remarkable leaf is the only one observed 

 in the collections. It is rather broadly lanceo- 

 late, about 16 centimeters long, and was 

 undoubtedly several centimeters longer when 

 perfect; the width at the broadest point is 

 about 5.5 centimeters. The. margin is deeply 

 undulate, and both lobes and sinuses are 

 broadly rourided. The midrib, as may be seen 

 from the figure, is extremely thick below, 

 where it exceeds a thickness of 3 millimeters, 

 but in the upper portion of the blade it is 

 reduced almost to the vanishing point. 



I am entirely at a loss to suggest the proper 

 generic reference for this leaf. The very thick 

 midrib and arching, camptodrome secondaries 

 suggest certain species of Ficus, but I do not 

 regard this resemblance as sufficient warrant 

 for placing it under this caption. For the 

 present it may remain as designated. 



Occurrence: Laramie formation, Marshall's 

 mine, Boulder County, Colo., collected by 

 N. L. Britton about 1885. 



Phyllites trinervis Knowlton, n. sp. 



Plate XXIV, figure 12. 



Phyllites trinervis Knowlton [nomen nudum], TJ. S. Geol. 

 Survey Bull. 696, p. 449, 1919. 



Leaf evidently thick and leathery, ovate, 

 broadly rounded below to an apparently 

 decurrent base, very obtuse and rounded 

 above; margin perfectly entire; triple-ribbed 

 from the extreme base of the blade, the ribs 

 of equal size, the middle one with about three 

 pairs of alternate, thin, much curved seconda- 

 ries, the lateral ones with several secondary 

 branches on the outside; all secondaries seem- 

 ingly camptodrome; finer nervation not re- 

 tained. 



The little leaf here figured is broadly and 

 very obtusely ovate, the length being 5 centi- 

 meters and the width about 4 centimeters. 

 The base is broadly rounded, with a slightly 

 decurrent portion through which pass the 



three ribs, their origin evidently being the top 

 of the petiole. Little of the other nervation is 

 Ipreserved, and this is well shown in the figure. 



The real affinities of this leaf are hard to 

 make out. It has, for example, exactly the 

 same type of base, as regards shape, size, and 

 nervation, as Ficus trinervis, a part of which 

 was formerly called Cinnamomum affine Les- 

 quereux, but the upper portion of the leaf is 

 wholly different. 



The basal portion of this leaf is also similar 

 to a form from Marshall that has been described 

 as Populus distortcc (p. 126), but it differs in 

 having the apex rounded instead of acumi- 

 nate. In general shape it suggests Populus 

 arctica Heer, as figured by Lesquereux, 87 but it 

 differs in details of primary nervation. It also 

 suggests one of the leaves. from the Bozeman 

 coal field described under the name Populus 

 cf. P- arctica Heer, 68 but the Bozeman leaf 

 differs markedly in the primary nervation. 



Occurrence : Laramie formation, Coal Creek, 

 Boulder County, Colo. 



Phyllites dombeyopsoides Knowlton, n. sp. 



Plate XVIII, figure 2. 



Phyllites dombeyopsoides Knowlton [nomen nudum], U. S. 

 Geol. Survey Bull. 696, p. 445, 1919. 



Leaf ovate, truncate or possibly slightly 

 heart-shaped at the base, regularly and ob- 

 tusely acuminate at the apex; margin .slightly 

 undulate, especially about the middle of the 

 blade; apparently triple ribbed from or near 

 the base of the blade, the central or midrib 

 very much the strongest, especially below, 

 with two pairs of strong, remote secondary 

 branches in the upper part; lateral ribs slender, 

 at an angle of about 60°, with a large lateral 

 branch in the lower portion, this with several 

 tertiary branches on the outside which arch 

 just inside the margin; lateral ribs forked 

 above, the branches passing to or near the 

 margin, the rib itself arching in a broad bow 

 and joining the lower secondary on the midrib; 

 intermediate secondaries and nervilles strong, 

 unbroken. 



This form is represented by the leaf figured 

 and several rather poor fragments. The ex- 

 ample figured, which lacks both base and apex, 



«' Lesquereux, Leo, The Tertiary flora: TJ. S. Geol. Survey Terr. 

 Rept., vol. 7, pi. 23, fig. 5, 1878. 

 » Knowlton, F. H., U. S. Geo]. Survey Bull. 105, pi. 6, flg. 7, 1892. 



