NATURAL SCIENCES OF PUILADELl'UIA. 155 



Bad Lands. Passing over the deep valley formed by this stream, we again as- 

 cend to a broad plateau which slopes gently away northward to the valley ot 

 the Shyenne. In the west the lofty range of the Black Hills is seen about sixty 

 miles distant, like a black cloud looming up above the horizon. Turning to the 

 left we descend about fifty feet into the basin of the Bad Lands, a large area 

 worn out as it were by the long continued action of atmosi)heric agencies, the 

 material having been carried away by Bear creek and another tributary of the- 

 Shyenne. After making our descent we pass over a portion of this denuded area 

 two or three miles in width, which is studded with low conical hills, on the 

 sides and at the base of which are numerous dull reddish silico-argillaceous 

 concretions, having much the shape and appearance of huge turtles. From these 

 concretions Messrs. Hall and Meek have described a remarkable Baculite, (B. 

 grandis,) a true Cretaceous fossil, the position of which is in the upper portioii 

 of a bed upon which the lowest stratum of the Tertiary basin of the Bad Lands 

 rests. 



Pursuing from thence a south-westerly course, we commence a gradual as- 

 cent and pass the junction of the two great Geological systems, the Cretaceous 

 and Tertiary, into the Titanotherium bed, the lowest member of this Tertiary 

 basin. We have, first, an ash-colored silico-argillaceous stratum with a green- 

 ish tinge, interspersed with large aggregated masses of particles of quartz, 

 passing up into a light gray calcareous grit. In my vertical section I have con- 

 cluded to throw all these strata, though presenting some lithological differences, 

 into one bed, from the fact that the remains of the huge Pachyderm that has 

 given it its name, are distributed to a greater or less extent all through it. T( 

 the Titanotherium may now be added another pachyderm discovered by the 

 writer in 1855, and described by Dr. Leidy under the name of Hyopotamiits ame- 

 ricanus. 



Passing over a nearly level denuded area about five miles in width, underlaid 

 by this bed, he came to the Turtle and Oreodon bed, so called from the im- 

 mense numbers of the remains of these animals found in it. This forms the 

 lower member of bed B of the vertical section, and is by far the most fossil- 

 iferous portion of the Bad Lands. Besides the remains of Oreodon and Testudo, 

 which are most abundant, many other species of vertebrates have been described 

 by Dr. Leidy from this bed. They are found in the debris on the denuded 

 plateau, or at the base of the Bluifs, and from the nearly perpendicular wall? 

 the Turtles often project like large colored concretions. Some of the Turtles 

 are of large size, measuring four feet in length and three to three and a half 

 feet in width. The most abundant species of Mammal appears to have been 

 the Oreodon Gidbertsonii, of which fragments of more than five hundred indi- 

 viduals have already been obtained from an area not over five miles square, 

 surrounding Ash Grove Spring, which is near the central portion of the Bad 

 Lands. 



The scenery is of the most remarkable and picturesque character. No 

 vegetation meets the eye, but on every side are high bare whitened walls, 

 and the traveller winds his way through these labyrinthine passages as 

 if in the gloomy apartments of some oriental sepulchre. Continuing our ascent, 

 we come to the dividing ridge between the Shyenne and White rivers, ranging 

 north-east and south-west through the central portion of the Bad Lands, in 

 which the little tributaries of these two rivers take their rise. Here the Turtle 

 and Titanotherium beds are concealed, and the upper members of this deposit 

 are well exhibited. Descending the slope toward White River the Turtle bed 

 again appears, and in the channel of White River a stratum of fine gray grit is 

 seen, the upper portion of the bed containing bones of Titanotherium Prouti. 

 Crossing White River we pass down the south side of the main body of the 

 Bad Lands, and find that on this side the beds consist mostly of outliers holding 

 a higher geological position than those at Bear Creek or Ash Grove Spring. 

 Near the entrance of Mule Creek and of several of the tributaries of White 

 River, are some beautiful exhibitions of the architectural features of the Bad 



1857.] 



