134 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



species — are variable in size, in the strength of the nervation, and in their 

 degree of perfoliation. Hence it is highly probable that the three species 

 described by Professor Heer from the arctic regions, namely, that cited 

 above, and his P. spectabilis and P. altemans (Fl. Foss. A ret., Vol. II, 

 Abth. IV, p. 480, PI. XLIII,fig. 15b; LIII, figs. 1-4, and LIV, fig 3), will 

 ultimately be combined in one. 



The specimens before us were brought by Mr. W. H. Dall from the 

 Yukon River, in Alaska. They show that the plant which bore them was 

 of strong, luxuriant growth, probably a tree of large size. No other 

 species is immediately associated with this in the collection made by Mr. 

 Dall, but the formation in which it occurs is undoubtedly of the same age 

 with that at Cooks and Admiralty inlets — the so-called Arctic Miocene — 

 and this tree formed a part of the luxuriant vegetation which included the 

 gigantic Querctis Grdnlandica, Ficus Alaskana, etc., and covered Alaska in 

 Tertiary times. 



Formation and locality: Tertiary (Miocene). Yukon River, Alaska. 



Phyllites cakneosus Newb. 



, PI. XLI, figs. 1, 2. 



Ann. N. Y. Lye. Nat. Hist., Vol. IX (April, 1868), p. 75; Ills. Cret. and Tert. PI. 

 (1878), PL XXVI, figs. 1, 2. 



" Leaves large, fleshy, and strongly nerved, orbicular in outline, 

 cordate or rounded, often unsymmetrical at the base, obtuse at summit, 

 margins wavy or coarsely and deeply scalloped; nervation strongly 

 marked throughout ; medial nerve straight, or nearly so, frequently pro- 

 duced into a long and strong petiole ; lateral nerves in six to eight pairs, 

 all more or less forked ; lower pair short and curving downward soon 

 after leaving the midrib ; second pair also curved outward near the base, 

 and reaching the baso-lateral margin by a course nearly at right angles 

 to the line of the midrib ; third pair strongest, much branched on the 

 lower side above the middle; upper pairs once or twice forked near the 

 summit; tertiary nerves parallel, simple, straight or gently arched, given 

 off at right angles from the secondary, which they connect." 



Collected by Dr. F. V. Hayden. 



Up to the present time I have failed to identify these leaves with 

 those of any genus known, living or fossil. In general form they resemble 



