36 



sas and Nebraska are referable, for their upper part, at least, to the Permian, 

 by their fossil remains of animals ; but as yet no fossil plants have been ob- 

 tained from them. The highest coal-beds in Kansas, those of Brownsville, for 

 example, have still in their shale species of ferns of the Carboniferous meas- 

 ures, not only the omnipresent species as Neuropteris loschii, N. hirsuta, 

 &c, but also Alethopteris serlii and Neuropteris rarinervis. In Franklin 

 County, of the same State, the coal also in the upper part of the Carbonifer- 

 ous measures is overlaid by an arenaceous shale, which has Asterophyllites 

 equiset'iformis, Pecopteris serrata, Lepidodendron, and other true Carboniferous 

 plants. Here is, for the western geological formations, the end of the flora of 

 the Paleozoic times. Except the two species of Catamites recorded from the 

 Permian of the Rocky Mountains, no fossil vegetable remains have been found 

 referable to a formation between the Carboniferous and the Cretaceous Da- 

 kota group. This remark could apply to the whole North American Conti- 

 nent, but for the few fossil plants known from the coal-measures of Richmond 

 and South Carolina, which by their characters are referable to the Triassic, 

 They mostly represent species of ferns with some large Equisetacea?, Cy- 

 cadece, and Conifers. And from what is known in Europe of the flora of the 

 formations between the Permian and the Cretaceous, the essential types 

 which have marked the character of the vegetation, by the predominance of 

 their remains, belong to the same families of plants. No trace of a leaf refer- 

 able to a dicotyledonous species has been recognized anywhere before the 

 Cretaceous. And even until the discovery of the vegetable remains of the 

 Dakota group, it was generally admitted that the first dicotyledon had ap- 

 peared in the middle or the Upper Cretaceous measures. 



A glance over the table of genera named above, as representing the es- 

 sential types of the flora of the Dakota group, is enough to show the prodigious 

 difference which separates this flora from those of any former epoch, even 

 considering the antecedent vegetation of the Jurassic, known as it is from 

 European specimens and European publications. The Ferns, Conifers, and 

 Cycadese, with a few species of Equisetacese, which constitute the whole flora 

 of that epoch, are all of peculiar types, without relation to any of the species 

 of the same families recognized as yet in the flora of the American Creta- 

 ceous. Of Ferns, this flora has an Hymenophyllum and Sphenopteris, whose 

 affinity is with Hpmenopliyllites furcatus of the Carboniferous, and still more 

 with a number of species of Hymenophyllum of our own time. Another 



