LESQUEREux.] PALEONTOLOGY LIGNITIC FLORA SPECIES. 397 



point, of attachment, appearing placed upon the slender stem, or rachis, 

 in a spiral order. They are of a thick consistence ; their surface cov- 

 ered with a coating of coaly matter, obliterating nearly every trace of 

 nervation An undefined medial nerve seems apparent on some leaves ; 

 but it may be a mere linear artificial depression. On other leaves, 

 deprived of epidermis, some thin strife running parallel and lengthwise 

 are recognizable. By the disposition of the branches and of the leaves 

 these vegetable fragments resemble those figured by Schimper as illus- 

 tration of the genus Ehisocaulon, Sap., (in Paleont. Veget., PI. Ixxx, Fig. S.\ 

 Habitat — Black Butte, burned shale above the main coal. 



POPTJLUS MUTABILIS, Hccr. 



One leaf only, representing a small form, (like that of Heer, Flor. Tert. 

 Helv., II, PI. Ixi, Figs. 9, 10.) The basilar veins are also attached to the 

 middle nerve, a little above the borders? and opposite, with three pairs of 

 alternate secondary veins above them, all in an acute angle of diver- 

 gence. The leaf, however, does not appear coriaceous. 



Habitat. — Black Butte. 



POPULUS HELIADUM, Ung. 



Leaves broadly-ovate, round-truncate to the base, long-petioled ; 

 borders entire, merely undulate toward the point ; lower secondary 

 veins open, marginal, thin, the upper ones parallel, close, simple, or fork- 

 ing once, ascending in an acute angle of divergence close to the borders, 

 where they curve. By its form, the direction of the lateral veins ascend- 

 ing straight to near the borders, &c., this leaf is similar to that described 

 by Unger, (Fl. v. Sotzka, p. 37, Tab. xv. Fig. 7,) differing, however, by 

 the secondary veins more numerous and at equal distance; a difference 

 which may be merely casual. 



Habitat. — Golden. 



Salix integea, a. Br. 



Leaves entire, linear-lanceolate, taper-pointed or acuminate, narrowed 

 or tapering to the petiole; lateral veins mostly opposite, in an acute 

 angle of divergence, the lowest pair less open than the upper ones, at 

 least in the leaves with a tapering base. 



We have specimens of Goldeu and of Black Butte ; in these last, the 

 leaves are more rounded to the ehort petiole, and the secondary veins are 

 all under the same angle of divergence. There is, however, no marked 

 difference, and both forms agree in their characters with the leaves of 

 this species as described by Herr, (Fl. Tert. Helv., II, p. 32, PI. Ixviii, 

 figs. 20-22.) The nervation of the leaves of Golden is the same as Fig. 21, 

 while the form of the leaves of Black Butte more closely resembles 

 Fig. 22. 



Habitat. — Golden and Black Butte. 



Myeica Torreyi, Lsqx., var. Minor. 



One leaf only has been found of this variety (?) Leaf shorter, shorter- 

 pointed, less gradually decreasing downward to the petiole; borders 

 denticulate, with close, smaller teeth. No other difference separates 

 this leaf from the typical form described from Black Butte in Report for 

 1872, (p. 392.) It is probably a mere local variety. 



Habitat. — Sand Creek, Colorado, A. Gardner. 



Betula gracilis (?), Ludw. 



Species represented by only one ovate, obtusely-pointed leaf, unequal 

 at the round subcordate base; borders crenulate; nervation campto- 



