12 ON THE GEOLOGY AND NATURAL HISTORY 
abruptly undulating, as well as in their lithological characters, and am now convinced that 
they belong to the upper members of the Tertiary, probably Post Pliocene, but yet holding 
a lower position than the yellow marls of the Missouri. 
July 22d. About two miles above our camp Loup fork cuts through undoubted Ter- 
tiary beds. The following section will show the strata in descending order: 
1. Yellowish brown laminated grit; effervescing with muriatic acid. 
bo 
. Similar to the bed above but of a deeper color and containing a greater per cent. of clay with numerous calca- 
reous concretions disseminated through it. 75 to 100 feet. 
8. Light brown clay, with many whitish particles like magnesia. 20 feet. 
4. Gray coarse grit, forming a heayy-bedded sandstone reaching to the water’s edge. 30 feet. 
In bed 2d I found fragments of the bones of mammals and turtles, and the whole series 
may be referred to the Pliocene period. 
At the mouth of Calamus river the strata are represented as follows: 
Yellowish brown grit. 12 feet. 
Iss) 
Limestone assuming a coneretionary form. 2 to 23 feet. 
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Caleareous clay quite indurated. 6 feet exposed above the water’s edge. 
Lieutenant Warren explored the Calamus fork for about 30 miles above its mouth and 
saw the same beds represented in the above section, sometimes with an aggregate thick- 
ness of fifty feet, and gathered from them numerous water-worn fragments of bones and 
shells of turtles. 
July 25th. Soon after leaving camp, a bed of arenaceous limestone was observed in 
several localities apparently containing traces of organic remains. There were many silici- 
fied tubes ramifying through the rock, which may have been the stems of plants, also many 
seeds like cherry-stones. Sometimes the rock becomes a partial conglomerate. The inco- 
herent material above and below the more compact bed, is a yellow marl. 
July 27th. Tertiary beds were observed throughout the day and a few bones and teeth 
were collected. 
July 28th. Passed over a country very similar to that of yesterday, but the high hills 
are becoming apparently more rugged. ‘They are cut through by numerous streams, form- 
ing ravines one hundred to two hundred feet in depth. ‘The sandhills are also appearing. 
July 29th. Passed through the sandhills all day. They have now become quite 
conspicuous, rising to the height of fifty to one hundred feet. 
August Ist. Measured the height of the sandhills from the bed of the Loup fork 
with a pocket level, and found that the highest point was about two hundred and twenty 
feet above the water level of the river. I think, however, that there is not so great a 
