The geographical distribution of animals, with a study of the relations ...

;chap, vii.] MAMMALIA OF THE NEW WORLD. 139and Upper Eocene, no remains of this order have been foundand in 1869, Dr. Leidy remarked on the small average size ofthe extinct North American mammalia, which were almost allsmaller than their living analogues. Since then, however, wonderfuldiscoveries have been made in depositsof Middle Eoceneage in Wyoming and Colorado, of a group of huge animals notonly rivalling the elephants in size, but of so remarkable andpeculiar a structure as to require the formation of a new order ofmammals—Dinocerata—for their reception.This order consists of animals with generalisedUngulate andProboscidean affinities. The lower jaw resembles that of thehippopotamus ;the posterior ;they had five toes on the anterior feet and four onthree pairs of horns, the first pair on the top of thehead, large and perhaps palmated, the second pair above the eyes,while the third and smallest stood out sideways on the snout.They had enormous upper canines, of which the roots enteredthe middle horn cores, no upper incisors, and small molars.Professor Marsh believes that they had no trunk. The remainsdiscovered indicate four genera, Dinoceras (3 sp.), Tinoceras(2 sp.), Uintatherium (1 sp.), and Eobasilcus (2 sp.). Many othernames have been given to fragments of these animals, and eventhose here given may not be all distinct.Another new order, Tillodontia, recently established by ProfessorMarsh, is perhaps yet more remarkable in a zoologicalpoint of view, since it combines the characters of Carnivora,Ungulata, and Rodents.These animals have been formed intotwo families, Tillotheridse and Stylinodontidae; and three genera,Tillotherium, Anchippodus, and Stylinodontia.Eocene of Wyoming and New Jersey.added ElotheriumAll are from thePerhaps to these must befrom the Miocene of Dakota, the other formsbeing all Eocene. They were mostly animals of small size,between that of the capybara and tapir. The skull resembled inform that of a bear ;the molar teeth were of Ungulate type, andthe incisors like those of a Rodent ; but the skeleton was morethat of the Ursidpe, the feet being plantigrade. Professor Copehas since described three new genera from the Eocene ofNew Mexico, Ectoganus, Calamodon, and Estlwnyr, comprising