NATURAL SCIENCES OF PHILADELPHIA. 157 



riner and more compact silicious character, and in others a coarser conglonae- 

 rate. These Hills are of considerable interest, as forming an intermediate link 

 uniting Bijou Hills to the main body of the Bad Lands. The two upper beds 

 of the vertical section are represented at this locality. The last outlier of 

 this deposit is seen at Bijou Hills on the opposite side of the Missouri 

 Rivor in lat. 43A°. These are a group of isolated hills towering high above 

 the surrounding country and forming prominent land marks for the voyager. 

 The two highest hills border upon the river and are from four to six hundred 

 feet in height. Farther into the interior are two other hills, the first about two 

 miles long, and the second about eight miles, ranging in a nearly east and west 

 course, sloping gently down toward the Coteau de Prairie. In the summer of 

 1853 I ascended one of the hills nearest the river in company with my friend 

 Mr. Meek, and, from a denuded portion near the summit, we obtained several 

 fragments of jaws and teeth belonging to two new species of mammals, which 

 have been described by Dr. Leidy as Ilipparion spcciosum and Merycadus nccaius. 

 In the autumn of 1856 I discovered on the denuded summits of the same hills 

 Hipparion occidcntalis and two new genera, Leptarctus primus, an animal allied 

 to the raccoon, and MerycMppus insignis, a remarkable new genus of ruminant 

 horse. These remains have all been described by Dr. Leidy in the Proceed- 

 ings of the Philadelphi;. Academy. 



The summits of these hills are capped with a bed of bluish-gray conapact 

 rock, quite variable in its character. Sometimes it is very fine, not unlike a 

 metamorphic rock ; again it is composed of an aggregation of particles of 

 granular quartz, interspersed with a few small water-worn pebbles; then 

 a coarse grained somewhat friable sandstone. Farther into the interior, 

 capping the summit of the long hill, this rock may be seen in places twenty 

 to thirty feet in thickness. The calcareous grits and marls underneath, may 

 be subdivided in descending order thus : — 



1st. — Yellowish-gray grit, with compact, fine calcareous concretions. 



'Ind. — Yellowish-white calcareous marl, containing great quantittes of the 

 comminuted fragments of bones. 



3;-c?. — Compact whitish calcareous clay, with a few vertebrate remains and 

 concreting limestone. The aggregate thickness of these beds I could not 

 determine, as the sides of the hill were, for the most part, covered with a 

 surface deposit of considerable thickness, sustaining a good growth of vege- 

 tation. 



The foregoing notes are designed merely as preliminary to a more thorough 

 description of the geological character of this most interesting deposit. Its 

 Miocene age and the Miocene affinities of most of the genera and species of fossils 

 yet obtained from it have already been discussed in an interesting paper by 

 Prof. Leidy, published in the Proceedings of the Academy for March, also 

 in a paper by F. B. Meek and the writer, published in the Proceedings for 

 April. 



The Zoological arrangement of the Catalogue is copied from Prof. Leidy's 

 paper published in March last. The object of the table is simply to show as 

 far as has been ascertained the stratigraphical position of the different 

 fossils, and the letters are made to correspond with those representing the 

 beds in the vertical section. 



The illustrative section accompanying this paper is intended to show the 

 relations of the Tertiary basin to the Cretaceous beds, and especially to 

 render more clear the connections of the widely separated outliers, Medicine 

 Hills and Bijoux Hills with the main body of the Bad Lands. 



1857.] 



