WAiii).] ((IIJ.KCTIONS KKOM THE FORT UNION GKOl'l'. 545 



to a height of about 600 feet. At numerous points along this escarii- 

 ment good exposures occur, and vegetable remains of one form or another 

 were seen at nearly all elevations. The lowest of the plant beds was not 

 over forty or tifty feet above the valley of the creek, and tlie plants here 

 consisted almost wholly of the large-leaved Sapiudus wliich is figured 

 on Plate L, Figs. 4-8. A few feet above this occurs a bed of conifer- 

 ous plants, and immediately above this one yielding a variety of Dicot- 

 yledons. Next in order is a stratum of heavy ironstone. This con- 

 tained a great number of seeds and fruits which are exceedingly curious, 

 but which are as yet wholly undetermined. Mixed with them are leaves 

 in a bad state of preservation belonging to the genus Platauus, and 

 probably to several other genera. 



The next bed that proved profitable to work was some 400 feet 

 higher. It was literally tilled with leaf impressions, and among these 

 was tiie immense Plataniis leaf, which is here figured natural size, Plate 

 XLI, Fig. 1. Here, too, were found the specimens of Ginkgo, which are 

 also reproduced in our illustrations, and which appear nearly identical 

 with G. adiantoides of (Jnger and quite too near the living plant. Not 

 less interesting was the discovery of the very perfect Sparganium lieads, 

 especially those borne on the original stem, one of the specimens of which 

 is shown in the illustrations (Plate XXXII, Fig. 6). 



Finally, in the white marl clitt' that forms the summit of the series of 

 terraces another florula was found, differing widely from all the rest 

 and characterized by the presence in great abundance of the remark- 

 able leaf which I have called Credneria daturcefoMa [Flate LVII, Plate 

 LVIII, Figs. 1-.5). Associated with this form were many leaves of Pop- 

 ulus and Corylus, which were obtained in profusion and in great per- 

 fection. This cliff showed evidence of having once been capped by a 

 yellow ferruginous sandstone containing fucoids. One much weather- 

 worn specimen was obtained. 



This remarkable series of plant-bearing beds begins at the base with 

 a light-colored and slightly arenaceous limestone, grows less calcareous 

 and more argillaceous and ferruginous until the ironstone bed is reached. 

 It then presents a series of alternating beds of limestone and ferrugi- 

 nous marl to the Sparganium bed, which is scarcely at all ferruginous. 

 The Credneria cliff consists of a soft, white, and nearly pure marl, 

 slightly tinted on weathered surfaces with iron oxide. The substance 

 of the leaves imbedded in this matrix is clearly visible, and gives the 

 impressions a very dark carbonaceous or lighter brown or lignite col- 

 ored appearance. 



Judging from the slight northerly di]) of the strata from the base of 

 the Laramie below Iron Bluff, where it is seen to rest on the Fox Uills, 

 and from Burns's Ranch, where the lowest strata lie beneath the bed 

 of the river, it seems probable that the summit of the Credneria cliff is 

 from 1,"J(»D to 1,.')00 feet above the base of the Laramie. 

 (> GEOL — —35 



