South Dakota School of -Mines 193 



especially the later ones, powerful horns or horn-cores. The skull 

 varies much in the different genera and species, considerably in 

 the different sexes, and individual variation is not uncommon. Its 

 full length in some of the larger species reaches as much as 

 three feet or even more. The width is generally less than two 

 feet, although in occasional skulls, especially of Brontotherium, 

 it may reach more than thirty inches. 



The horn-cores are more or less cellular at the base and are 

 placed transversely and project upward and outward. Their size, 

 shape and position, like other parts of the skull, vary much with 

 species and sex. The ears are placed far to the rear, while the 

 eyes are surprisingly near the front. The brain, like the brain 

 of nearly all early mammalian types, was very small. The teeth, 

 usually thirty-eight, were large. This is particularly true of the 

 grinders in the, upper jaw. Not infrequently in the larger 

 species the well-fanged, nearly square upper molars measured 

 more than four inches in diameter. Plate 38 is a reproduction 

 of the teeth as given by Marsh in the American Journal of 

 Science many years ago. The neck was short and stout and the 

 head in ordinary position was evidently held declined. The Ti- 

 tanothere was a perissodactyl and a pachyderm. The nature 

 of its thick skin is not positively known, but relying on skeletal 

 characters common to thick-skinned animals, the restorations 

 that have been made, such as are reproduced in Plates 39 and 40, 

 are believed upon considerable evidence to be within reasonable 

 limits of accuracy. 



Notwithstanding the abundant Titanothere remains that 

 have been found, complete skeletons are rare. Hatcher in 1902, 

 gives the total number in the whole country as four, as follows : 

 One in the Carnegie Museum, from War Bonnet creek, north- 

 western Nebraska ; one at Yale University, from near Chadron ; 

 one in the American Museum of Natural Histry, from the Big 

 Badlands; and one in Princeton Museum from the Big Bad- 

 lands. Of these the Carnegie Museum skeleton is from the 

 Lower Titanotherium beds, the other three from the Upper 

 Titanotherium beds. 



ELOTHERIDAE AND DICOTYLIDAE. 



Few fossil animals of the region of the Black Hills have 

 afforded more real puzzling features than the ancestral swine. 

 Several genera and a number of species have been identified, 

 including several classed as ancestral peccaries, but usually the 

 material is fragmentary and confined mostly to the head and 



