DAKOTA AND NEBRASKA. ' 355 



ancient Dakotean and Nebraskan waters teemed with such a'n abundant provision of 

 savory ruminating hogs? 



The tertiary mammals of Dakota and Nebraska, the subjects of consideration in 

 the preceding pages, are not remarkable for large size, compared with those of later 

 periods including the existing one. Indeed, the White River miocene f^iuna is rather 

 remarkable for the reverse character, most of the animals having been of compara- 

 tively small size. Among the carnivora there was a single large one, the Hyccnodon 

 horridus, which was about equal to a full-grown Black Bear. The feline animals 

 were small. Among the vegetable feeders there was only one animal of compara- 

 tively large size, the Titanotherium Prouti, winch approached in bulk the living 

 Elephants. In the pliocene fauna of the Niobrara there were a greater number of 

 large animals than in the former. Besides a Horse as large as the domestic species, 

 it contained a Rhinoceros about the size of the living Indian species ; a large rumi- 

 nant, Megcdomeryx ; a Mastodon; and an Elephant, as large as any elsewhere dis- 

 covered. The other remains generally indicate animals of small size compared with 

 later congeneric species, both extinct and recent. 



An interesting fact, which, however, might have been anticipated in view of the 

 theory of the origin of species through successional development, is the nearer 

 approach to uniformity in the general physiognomy of the animals of the various 

 orders of both of the extinct faunte which have been the subjects of consideration, 

 than in animals of corresponding relationships in later faunae. In the general form 

 of the skull, especially in the shape and construction of the cranium, with temporal 

 fossae separated alone by a sagittal crest, in the absence of horns or horn-like 

 appendages, and in the number, kind, and arrangement of the teeth, the tertiary 

 mammals of Nebraska and Dakota exhibit a decidedly neai'er relationship with one 

 another than the mammals of corresponding or allied families of later epochs. 



The White and Niobrara River faunte are clearly consecutive, the former being 

 older than the latter. In view of the apparent relationship of the animals, I have 

 considered the faunae to be successively of miocene and pliocene age, though it has 

 not been positively ascertained that they were actually cotemporaneous with these 

 epochs, as recognized elsewhere. 



The better known miocene and pliocene formations of other localities in North 

 America are almost entirely marine in character, and, though rich in the evidences 

 of animal life, have yielded but few remains of terrestrial mammals, so that we are 

 unable to make comparisons between their faunae and those above mentioned. 



The following table exhibits comparative lists of the terrestrial mammalian faunas 

 of the miocene, pliocene, and quaternary periods of North America. The mammals 

 of the two former periods are almost all represented by the remains from Dakota and 

 Nebraska, which form the main material of the preceding pages. Representatives 



