UNGULATES 211 



if the assumption is true, the certainty of wear and the equal certainty 

 that the parts of the individual skeleton would have been widely sepa- 

 rated instead of occurring near together, the assumption has always 

 seemed highly improbable, but the doubt was sufficient to turn the scale 

 in favor of conservatism. Lately a very perfect upper molar of a horse, 

 corresponding in size to that indicated by the fossils from Afton Junction, 

 has been found in true Aftonian beds, associated with the typical Afto- 

 nian fauna, the mammalian remains showing the usual Aftonian phase of 

 fossilization. The molar (plate 19, figures 5-7) belong to the genus Hip- 

 parion, and the enamel pattern is somewhat like that of Hipparion gratum 

 Leidy. The specific determination is, however, left for the present unset- 

 tled. The tooth was taken from the Whitham gravel pit in section 22, 

 township 64 north, range 41 west, south of Eockport, Missouri. A con- 

 siderable amount of material from this pit has been scattered and lost ; in 

 the small collection in hand the true horse, Equus, is represented by one 

 metatarsal, four lower molars, and one worn upper molar. This last 

 measures 33 millimeters in transverse diameter, agreeing in size and in 

 other characters with the teeth, which have been referred to Equus scotti 

 Gidley. A large camel is represented by one premolar ; there is a grinder 

 of Elephas columbi, the common Aftonian elephant, and there is a part of 

 a large tusk. The Hipparion molar is fresh and unabraded, and, while 

 not making it absolutely sure, it increases the probability that the small 

 equine fossils from the Afton Junction-Thayer region belong to a member 

 of the true Aftonian mammalian fauna. Hipparion venustum Leidy, 

 originally described as Hippotherium venustum,^ is credited to the post- 

 Pliocene, and it was found associated with Equus, Elephas, Mastodon, 

 Castoroides, Mylodon, and other characteristic Pleistocene types. 



DEER 



A metacarpal from Turin, a part of the lower jaw with molars from the 

 Cox pit, and some other less satisfactory fragments of the cervine skeleton 

 from different localities indicate an animal closely related in size and 

 structure to the modem Virginia deer. 



CAMELS 



The new collections contain foot bones and teeth of mammals belong- 

 ing to the Camelidae. There are toe bones corresponding in size to that 

 illustrated by figure 1, plate 21, of the first paper; but there is one 

 proximal phalanx from Aftonian gravel at Hinton station, near Council 

 Bluffs, which is much stouter and heavier than that represented in the 



* Description of vertebrate fossils, by Joseph Leidy, in Holmes' post-Pliocene fossils 

 of South Carolina. Charleston, 1860, p. 105, pi. xvi, figs, 32, 32a, 33, 33a. 



