l893-J FAIRCHILD — EVOLUTION OF UNGULATE MA^L^L•\LS. 209 



There are but three families now living, represented by the 

 Horse, Rhinoceros, and Tapir, but these are closely connected by 

 numerous extinct forms. Cope enumerated (1883) one hundred and 

 ninety-two species, of which nineteen are living. He regards his 

 Systcmndou and Ectocion as parent types. 



The complete pedigree of the Horse has been traced by Marsh, 

 from the little Eoliippiis, of the lower Eocene, with four toes and the 

 rudiment of the first on the fore feet, and three on the hind feet, 

 through seven intermediate genera of successive horizons in the 

 Tertiary, to the modern genus, Equus, in the upper Pliocene. 

 Miohippus, from the lower Miocene, resembles Anchitheriiim I.eidy, 

 and Protohippus of the upper Miocene most resembles Hipparioii. 

 Marsh finds some forty extinct species in this group. It is certain 

 that the hor-<e originated in America, and roamed over both conti- 

 nents in Post-Tertiary time, and then for an unknown reason became 

 extinct. 



The Paleothcrium is closely related to the early members of 

 the Horse family, and Cope includes here some of the supposed 

 ancestors of the horse. The family is entirely extinct since the 

 Pliocene. 



The Rhinoceros family has many representatives and a long 

 line of ancestry in the Tertiary. Ca'nopus from the Miocene of 

 America is the earliest member of the family, of which there seem to 

 have been two branches. Diceratherimn had a transverse pair of 

 horns on the nasal bones. Several species are found in American 

 Pliocene, but none later. The living species have three toes on each 

 foot, and horns on the median line. 



The Tapirs constituted another family of American origin. It 

 began in the Eocene, and exists to-day in South America and East 

 India. They have three toes on the hind feet, with four on the fore 

 feet, but the axis of the arm passes through the third digit. It is the 

 most generalized type of living Perissodactyla. 



The Titanotheriiim family is found only in the upper Eocene and 

 lower Miocene of the American lake-beds. 



Of the Lophiodontidae Cope enumerates fifty species, all from the 

 Eocene of America and Europe. They vary in size from that of a 

 Rabbit to that of an Ox, and resemble most, among living aaimals, 

 the Tapirs. 



The paper was illustrated by exhibition of fossils and lantern 

 views. 



