570 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



described is a sandy marl of ashy color, and of 80 or more feet in thick- 

 ness. This is interrupted below the middle, in the locality under con- 

 sideration, by two thin beds of impure lignite, of from 2 to 4 feet in 

 depth and 10 feet apart ; stems and fragments of leaves are abundant in 

 them; the color is of various shades of brown. On the summit of the 

 gray beds is another stratum of rather soft pale brown or rusty sand- 

 stone, of from 12 to 20 feet in thickness, which contains great numbers 

 of shells, usually of small size, but occasionally larger. 



From the horizon of undouDted Dinosaurian remains above mentioned 

 to and including the sandstone just described, the deposits are of fresh- 

 water character. 



Immediately above the basal sandstone, teeth of herbivorous and car- 

 nivorous Dinoscmria occur, with ChampsosaMnis and scales of Gar-fishes 

 and bones of numerous Turtles, presumably of lacustrine habitat. Imme- 

 diately below the upper sandstone, a bed of Uniones is constantly pres- 

 ent, which varies from 1 to 60 or 70 feet in thickness, and sometimes 

 replaces the small Viviparas and Physas which fill more or less of the 

 sandstone. In some places, the Uniones and their debris occupy the 

 entire depth of the formation, the shells being in some places broken up 

 and scattered, having somewhat the effect of mica mingled with the 

 arenaceous marl. Fragments of Vertebrate animals are abundantly 

 mingled with the Uniones, the greater part of the species described 

 in this report having been found at this horizon ; perfect bones are rare 

 in it, and the skeletons appear to have been separated and the single 

 bones often broken up before being deposited. The teeth are usually 

 found separated from the jaws, but only occasionally do they exhibit 

 any appearance of having been rolled. 



There are in some places thin beds of a reddish-brown chcity rock in 

 this series, which break up and cover the slopes and ledges with thou- 

 sands of angular fragments. This feature, with the alternating marly 

 and sandstone beds, with their light colors, together with the fractured 

 condition of the fossils, constitute points of resemblance to the Wahsatch 

 formation of New Mexico. A section of the Judith Eiver beds as they 

 appear In the bluff, adjoining that represented in diagram in Fig. 2, is 

 represented by Fig. 3, Plate 31. 



As already observed, the beds, here called No. 6 (Judith Eiver epoch), 

 acquire toward the center of the basin a much greater relative thickness. 

 The section now given derives interest from the fact that it represents 

 the beds near their borders, where the transition from the marine to 

 lacustrine deposits can be studied. The locality is also interesting from 

 the fact that both classes of Vertebrate fossils were found in place on the 

 same escarpment. This cannot always be observed, since, in the very 

 few cases where the series of rocks is complete, fossils may be wanting 

 from the one or the other horizon. Thus the Vertebrata of marine char- 

 acter already enumerated as occurring immediately above the No. 5 

 sandstone, belong to the same bed (which is more than 100 feet in thick- 



