TRANSACTIONS OF SECTION C. 681 



arrows. On allowing water streaked with colouring matter to flow over it from 

 two areas, supposed to represent tlie great gathering grounds of snow of the Glacial 

 period, the water had taken paths, as shown by coloured streaks, corresponding to 

 those taken by the ice, as shown by the arrows. 



2. Fotes on the Cromer Excursion. By Clement Reid, F.G.S. 



3 On the Tertiary Lacustrine Formations of North America. 

 By W. B. Scott. 



The early French explorers in the western parts of North America discovered 

 certain large areas of e.xtraordinarily broken and difficult country which thej-^ 

 called 'mauvaises terres a traverser'— a term which has been translated and 

 shortened into the modern phrase 'bad lands.' Geological examination soon 

 showed that these areas were covered with fres^h-water deposits of Tertiary age, and 

 that they represented a .series of great lakes in which were entombed a vast 

 number of representatives of the vertebrate faunas which successively occupied the 

 country. 



I. (1) The most ancient of these formations is the Puerco, which overlies with_ 

 apparent conformity the Cretaceous. This rather small lake occupies parts of 

 Southern Colorado and North-western New Mexico. (2) The Wasatch succeeds 

 after an interval and was much larger : it extends from New Mexico into Northern 

 Wyoming. At least two contemporaneous lakes represent this horizon, and at the 

 south its strata lie upon the Puerco. (3) The Bridger is indicated by a much 

 smaller series of lakes, in W^yoniing, Utah, and Colorado, which seem to have been 

 successive rather than contemporaneous, and has been divided into tliree stages : 

 (a) Wind Puver, (6) Bridger, {c) Wasliakie. The Wasatch beds pass under the 

 Bridger at very many points. (4) Extensive orographic movements followed^ the 

 Bridger stage and led to the formation of a new lake basin in Northern Utah, 

 overlying the Bridger — the Uinta. Osborn has shown that two distinctly marlied 

 horizons occur within the limits of the Uinta. (5) The Uinta was the last of the 

 great bodies of fresh water in the region to the west of the main chain of the 

 Rocky Mountains. The movements now affected the Great Plains region, and an 

 enormous lake was developed which extended along the eastern front of the 

 moimtains from Nebraska into North Dakota, together with a second basin in 

 Canada. This is the White l\iver formation, which is plainly subdivisible into 

 three horizons — the I'itanotherium, Oreodon, and Protoceras beds. (G) This was 

 followed by the Jolm Day, which is mostly confined to Oregon, but a second 

 very smalf basin occurs also in Central Montana. (7) A considerable hiatus 

 separates the .lohn Day from the overlying Loup Fork, which is by far the niost 

 extensive of all the Tertiary lakes, and covers nearly all the Plains region, fiota 

 South Dakota far into Mexico. It is not yet certain whether this was one vast 

 body of water or a connected series of lakes. Independent basins occur in Montana, 

 Nevada, and Oregon. In these the Loup Fork overlies the John Day unconform- 

 ably, as farther east it overlies the White River. The Loup Fork falls naturally 

 into three horizons, separated both by their faunas and more or less marked uncon- 

 formities : {a) Deep River, only in Montana ; {b) Nebraska, the principal area pf 

 the Plains region ; (e) Palo Duro, known in Kansas, but principally developed in 

 Texas. (8) In the Indian territory and Texas, in places overlying the Palo Duro, 

 occurs the Blanco, the boundaries of which have not been traced as yet. (9) 

 Occupying the surface of most of the Great Plains region are the uncompacted and 

 obscurely stratified Equus beds, which re.st unconformably upon all other forma- 

 tions of the region, from the Cretaceous to the Pliocene. 



II. The Lacustrine beds have for the most part retained their horizontal 

 position, only rarely being tilted. They are composed of felspathic muds, clays, 

 sands, and conglomerates, generally cemented by some calcareous compound, and 



