406 GEOLOGICAL SURVEY OF THE TERRITORIES. 



tantly dentate ; borders entire downward to the base; nervation camp- 

 todrorae ; secondary veins parallel, in an acute angle of divergence, 

 ascending nearly straiglit to the borders, where they curve and which 

 they follow, entering the teeth by their divisions. From B. Merianiy 

 Heer, as represented in Fl. Tert. Helv., (Ill, p. 82, PL cxxvi, Figs. 5-11,) 

 this leaf differs by its oblanceolate or Ungulate form, the veins more 

 straight and on a more acute angle of divergence, and the borders entire 

 from under the dentate acumen. There is, however, a marked differ- 

 ence in form and nervation in the numerous leaves of this species, as 

 figured by Heer, {loc. cit.;) therefore tbe separation into a new species of 

 this only leaf, whose characters are so closely related to those of the 

 European form, is questionable. 



Habitat. — Black Butte ; in shale, above the main coal. 



SPECIES OF THE SECOND GROUP. 



POPULUS ARCTiCA, Heer. 



This species has been already mentioned from the Washakie group, 

 Medicine Bow, Carbon, &c., (Reports for 1871 and 1872.) but not de- 

 scribed. The present form appears to be the most common in the Lignitic 

 measures. Leaves coriaceous, entire or undulately crenate, round or 

 more enlarged on the sides and reniform, obtuse, or obtusely short- 

 pointed, truncate at base; nervation 7-palmate from the top of the 

 lietiole ; middle nerve crossed by strong nervilles at right angle, with 

 two pairs of secondary veins in its upper part; inner pairs of basilar veins 

 curving inward in j)assing up toward the point where they join the 

 branches of the middle nerve ; lateral basilar veins ramified outside, 

 except the lowest pair, which is simple and marginal, all distinctly 

 camptodrome. The two specimens from the locality indicated below 

 have the same form of leaves as those in Heer's Fl. Arct. (PI. v. Fig. 3,) 

 one with the borders nearly entire, the others with crenulate borders. It 

 appears generally distributed in the whole thickness of the Lignitic 

 measures, except in the first group, where it has not yet been discovered. 



Habitat. — Troublesome Creek, Colorado, Mitchell. 



Platanus dubia, SI), nov. 



This form, represented by a large number of specimens, corresponds 

 evidently with the description of P. nobilis, ISTewby., in Extinct Floras 

 of North America, (p. 67.) In this last species, however, the lateral and 

 basilar nerves are described as straight and parallel, terminating, and 

 their branches also, in the teeth of the margins. In the new species or 

 variety, jyer contra, the leaves are perfectly entire, and the secondary 

 veins and their divisions are all camptodrome, or curving near the borders, 

 and following them in festoons. It is probable that this difference is 

 merely casual. One of the specimens from Troublesome Creek shows 

 the close secondary veins camptodrome along the borders of the inner 

 side of the lobes, while on the outside a few of them teminate in small 

 teeth, and are therefore craspedodrome. This remarkable species, which 

 seems rather related to some southern forms of Araliacew than to Flata- 

 nits, and which too is related by form and nervation to the Sassafras 

 leaves of the Cretaceous, has apparently, like these, two distinct kinds 

 of nervation and of border-leaves, resulting from the disposition of the 

 secondary veins. 



Habitat. — The specimens, all presenting the same characters, are from 

 Mount Brosse, Dr. Hayden; Willow Creek, Holmes; Troublesome Creek, 

 Mitchel. The distribution of this species appears to be limited to few 



