VERTEBRATE LIFE IN AMERICA. 685 



that the Cameloid type of ruminant had already become partially 

 specialized, although there is a complete series of incisor teeth, and 

 the metapodial bones are distinct. In the Pliocene, the camel tribe 

 was, next to the horses, the most abundant of the larger mammals. 

 The line is continued through the genus JProcamelus, and perhaps 

 others, and in this formation the incisors first begin to diminish, and 

 the metapodials to unite. In the Post-Tertiary we have a true Auche- 

 nia, represented by several species, and others in South America, 

 where the alpacas and llamas still survive. From the Eocene almost 

 to the present time, North America has been the home of vast num- 

 bers of the Camelidce, and there can be little doubt that they origi- 

 nated here, and migrated to the Old World. 



Returning once more to the upper Eocene, we find another line of 

 descent starting from Oromeryx, which, as we have seen, had appar- 

 ently then just become differentiated from the older Bunodont type. 

 Throughout the middle and upper Miocene, this line is carried for- 

 ward by the genus Leptomeryx and its near allies, which resemble so 

 strongly the Pliocene Cervidce that they may fairly be regarded as 

 their probable progenitors. Possibly some of these forms may be re- 

 lated to the Tragididce, but at present the evidence is against it. 



The deer family has representatives in the upper Miocene of Eu- 

 rope, which contains fossils strongly resembling the fauna of our 

 lower Pliocene, a fact always to be borne in mind in comparing the 

 horizon of any group in the two continents. Several species of Cer- 

 vidce, belonging to the genus Cosoryx, are known from the lower Pli- 

 ocene of the West, and all have very small antlers, divided into a 

 single pair of tynes. The statement recently published, that most of 

 these antlers had been broken during the life of the animals, is unsup- 

 ported by any evidence, and is erroneous. These primitive deer do 

 not have the orbit closed behind, and they have all the four metapodial 

 bones entire, although the second and fifth are very slender. In the 

 upper Pliocene, a true Cervus of large size has been discovered. In 

 the Post-Tertiary, Cervus, Alees, and Tarandus, have been met with, 

 the latter far south of its present range. In the caves of South Amer- 

 ica, remains of Cervus have been found, and also two species of ante- 

 lopes, one referred to a new genus, Leptotherium. 



The hollow-horned ruminants, in this country, appear to date back 

 no further than to the lower Pliocene, and here only two species of 

 Itison have as yet been discovered. In the Post-Tertiary this genus 

 was represented by numerous individuals and several species, some of 

 large size. The musk-ox ( Ovibos) was not uncommon during some 

 parts of this epoch, and its remains are widely distributed. 



No authentic fossil remains of true sheep, goats, or giraffes, have 

 as yet been found on this continent. 



The Proboscidians, 1 which are now separated from the typical 



1 Proboscidea, the mammalian order which contains the elephants, and extinct masto- 

 don and mammoth. 



