1866.] 293 fHayden. 



special geographical names,* indicating points where each division is 

 shown in its largest development. No. 1 is called the Dakota group, 

 because it was first described along the Missouri River, near Dakota 

 Territory, and there exhibits its typical characters. No. 2, or Fort 

 Benton group, has a thickness of 800 to 1000 feet near Fort Ben- 

 ton, while along the Missouri River, near the mouth of the Vermil- 

 ion, where it was first discovered, it never attains a thickness of more 

 than 80 or 90 feet. No. 3 is called the Niobrara group, as it presents 

 its typical characters and is most finely shown along the Missouri, 

 near the entrance of the Niobrara River. No. 4 is named the Fort 

 Pierre groii^, from the fact that this point is located near the centre 

 of its greatest thickness. No. 5 is denominated the Fox Hills group, 

 from an elevated ridge between Moreau and Grand Rivers, where it 

 contains a great abundance of its characteristic organic remains. 

 This ridge continues a little east of north, crossing the Missouri 

 River near the mouth of Cannon-ball River. All these divisions 

 reappear along the slope of the mountains, showing quite clearly that 

 they dip beneath the Tertiary beds in the basin-like form before de- 

 scribed. 



Then come the great Tertiary basins, which may be given in the 

 order of their supposed age, commencing with the oldest : 1st. The 

 Judith River Basin occupies an area of about 40 miles in length from 

 east to west, and 15 to 20 from north to south. 2d. The Great Lig- 

 nite Basin occupies all the country from Heart River to the Mussel- 

 shell, most of the Valley of the Yellowstone, extends for an un- 

 known distance northward, into the British Possessions, and south- 

 ward at least to the North Platte, and it is supposed that the Lignite 

 beds near Pike's Peak and Raton Pass, in New Mexico, are of the 

 same age. The limits of this great basin have not yet been strictly 

 defined. 3d. The Wind River deposits occupy an area of about 100 

 miles in length and 40 to 50 in breadth. 4th. The Basin of the 

 " Mauvaises Torres," or Bad Lands, of White River, cover a vast 

 region, at least 100,000 square miles, and from the scattered hills 

 on both sides of the Missouri River, this great fresh- water lake must 

 have spread over 150,000 square miles. It is supposed, from the 

 evidence already secured, that these lakes were not contemporaneous, 

 but succeeded each other in the order enumerated. 



Dr. H. remarked, in regard to the probable existence of Coal in 

 the Coal measure rocks from Leavenworth City to Omaha, he be- 



* Meek and Hayden, Proceedings Academy Nat. Sciences, 1861. 



