OF THE UPFER MISSOURI. 
93 
a greater or less extent over the prairie, resting upon Cretaceous formation No. 5 of the 
vertical section. At Long lake the Lignite Tertiary begins to assume considerable impor¬ 
tance. On the left side of the Missouri from a series of denuded hills we have the follow¬ 
ing section of strata in descending order. 
Feet. 
1. Yellow and drab arenaceous grit, . . . . . . . . . . . . 20 to 30 
2. Impure lignite, ................ 1 
3. Gray arenaceous grit, indurated, contains a small portion of clay, also vertebrate remains, as Compsemys 
victus, Emys obscurus, Trionyx , &c., ............ 40 
4. Impure lignite of a reddish color, with somewhat the character of a carbonaceous clay, .... 4 
5. Rather fine-grained gray silicious grit, with a slight admixture of clay, contains great numbers of dull red 
argillaceous concretions, fragments of turtles mentioned in bed 3, and the bones of a huge deinosaurian, 
described by Dr. Leidy as Thespesius occidentalis, . . . . . . . . . 30 to 50 
The lowest bed of the above section rests directly upon the well-known Cretaceous 
formation No. 5 of the vertical section. Bed 5 is the same yellow sandstone seen near 
Fort Clark, which there contains so many freshwater and estuary shells. On the Square 
hills, thirty miles below Fort Clark, it becomes a heavy-bedded, coarse-grained, ferrugin¬ 
ous sandstone, containing Paludina, Melania Nebrascensis , M. Warrenana , and Corbula 
mactriformis. 
Near Apple creek on the Missouri, in a bank cut by the river, we have the following- 
section of beds in descending order. 
Feet. 
1. Deep yellow grit, with some clay, caps the hills. 
2. Yellow sand, passing down into a gray and dark gray grit, ......... 40 
3. Impure lignite, with a shaly structure, ............ 1 
4. Drab indurated arenaceous clay, ............. 8 
5. Impure lignite; 2 feet. First appearance of lignite immediately along the river. 
6. Gray and dark gray grit, ............... 30 
Underneath the Tertiary bed 6 comes a layer of yellow arenaceous and argillaceous grit, 
containing several species of Pectuncidus, Fnsus, See. This is undoubtedly the upper por¬ 
tion of No. 5 of vertical section, though its fossils all have a peculiar Tertiary aspect. 
Indeed all the mollusca from formation No. 5 approximate so closely to well-known Ter¬ 
tiary forms, that I am inclined to consider it a transition or bed of passage from the 
Cretaceous to the Tertiary epoch. 
At Fort Clark we have a bed of lignite, two feet in thickness exposed, presenting its 
usual characters. 
1. Ferruginous sandstone, 30 to 40 feet. Near the base of the sandstone is a seam eighteen inches in thick¬ 
ness, composed of shell-marl, with fine specimens of Paludina , Melania, Corbula, &c. These shells are 
