6 CRETACEOCTS AND TERTIARY FLORA. 



Conifer. The fragments referable to this group are difficult of determina- 

 tion, for the organs represented upon the coarse shale or hard ferruginous 

 sandstone of the formation merely expose some traces of their more prom- 

 inent outlines, originally printed upon the soft embedding matter. We do 

 not find, therefore, any flattened cones with the scales, nor any flattened 

 branches with leaves, but impressions only, more or less deeply carved 

 into the stone, the cones, even passing vertically or obliquely through the 

 shales and showing the space originally occupied, as a mere cylindrical 

 hollow, around which the forms of the scales are more or less clearly 

 molded. The numerous leaves of Pinus spread upon the surface have dug 

 in the same way, and by their hard substance, narrow linear channels, 

 representing the back of these leaves, with an indistinct midrib; and 

 branchlets of Sequoia also are seen as longitudinal grooves, bearing on 

 both sides the same impressed form of their leaves. This cannot be con- 

 sidered a very distinct representation of characters, the minute details 

 desirable for an exact determination being more or less obsolete. 



Among the specimens recently examined, a second fragment has been 

 found referable to PhyUocladus. 1 The presence of this genus in the Cre- 

 taceous flora is thus sufficiently ascertained. We may, therefore, record 

 as recognized in the flora of the Dakota Group, for the Ferns, the genera 

 Lygodium, Sphenopteris, Hymenophyllum, and Gleichenia, the first three by 

 each one species, the last by two; in the Cycadece, Podozamites by six 

 species, and in the Conifers, Sequoia by three species, Pinus by one, Phil- 

 locladus by one, Torreya and Thuites each by one, leaving out as of uncer- 

 tain generic relation with the cones mentioned above, Glyptostrobus (?) 

 gracillimus, which is perhaps identifiable with Sequoia condita, or with 

 Frenelites, and Geinitzia (?) , known merely by the impressions of some 

 detached scales. To this should be added Araucaria from a species 

 described in "Extinct Floras of North America" by Dr. Newberry, from 

 Nebraska specimens. 



The first dicotyledonous leaves described in the "Cret. Fl.," under 

 the name of Liquidambar integrifolium, have been considered by some 



'Since this was written, Heer, in part 2d of Vol. VI of the "Arctic Flora," has described this species 

 under the name of Thinfieldia Lesquereuxiana, as a plant of uncertain relation. 



