534 FLORA OK Tin; i.ak'amii: gkoip. 



it must certainly possess weight in the general problem of geologic age. 

 It is also noteworthy that this form conies from the Fort Union beds 

 on the Lower Yellowstone, and from one of the highest strata of this 

 formation that are represented in that section. 



There occur in the collections a large number of querciform leaves, 

 probably for the most part referable to the Cretaceous genus DryophyUum, 

 establisiu'd by Debey as the receptacle for the numerous archaic oaks 

 which he found in the iron sands of Aix-la-Chapelle. Until quite lately 

 this geiuis was very little known, and chiefly from specimens furnished 

 by him to ditierent museums in Europe, but within the past two years 

 he has published a small pamphlet with one plate, illustrating several of 

 the forms.' The material seemed rather obscure and fragmentary, and 

 the figures are very rude, but they enable us to gain a better idea of 

 the limits of the genus than was otherwise jjossible. We have from 

 the Laramie group forms closely allied to several of Debey's species of 

 DryophyUum, such as D. Eodrys, D. [/racile, D. tretaceum, D. Aquisfjra- 

 nense, etc., although it is hardly probable that any of these species 

 actually flourished in America. 



There can scarcely be a doubt that we have in Figs. 8 and 9, Plate XL, 

 the Cretaceous species Platanus Heerii of the Dakota group and arctic 

 Cenomanian strata. Compare, for example, flg. 1 of plate vii, in the 

 sixth volume of Heer's " Flora fossilis arctica," Part II, Cretaceous flora 

 of Greenland. 



Several forms of Hedera have a Cretaceous aspect, and it is quite 

 probable that H. primordialis, Heer, from the Greenland beds at'Atane, 

 may be represented by our Fig. 4, Plate XL VIII. 



In Fig. 1, Plate LX, we have a form which, for so much of the leaf 

 as is present, resembles the figures of similar portions of Heer's Populus 

 8tygia (Fl. foss. arct., Vol. Ill, Kreidefl. v. Gronland, plate xxix, fig. 

 10; Vol. VI, Abth. II, Kreidefl. v. Gronland, plate xvii, figs. 5, 7; 

 plate xxxix, flg. 5). But for the great resemblance to these flgiu-es, I 

 should have certainly regarded it as a Liriodendron, and notwithstand- 

 ing this resemblance I am inclined to refer it to that genus. But Lirio- 

 dendron is rather a Cretaceous genus, although the broad-leaved forms 

 like this occur also in later strata and form the type to which the living 

 species belongs. 



I have not mentioned the singular cryptogamous form that was col- 

 lected both at Iron Bluff and at Burns's Ranch, although I am now con- 

 vinced that it is a Cretaceous form, because up to the time when it was 

 necessary to submit this paper it had not been sufticiently studied and 

 the drawings were incomplete ; but upon careful comparison I am sat- 

 isfied that it is the same plant that is figured by Dawson in his paper 

 in the Transactions of the Royal Society of Canada (plate i, fig. 3) as 



1 Sur lea feuilles querciformes des sables d'Aix-la-Cbapelle, par le Dr. M. Debey, 

 d'Aix-la-Cbapelle. Extrait du Coinpte rendu du Congrfes de botanique et d'borticul- 

 ture de 1380. Deuxieme partie. Bruxelles, 1881. 



