166 TEN years' progress in vertebrate paleontology - 



of the American Cervidse. The Oligocene genus Leptomeryx is regarded 

 as of primitive unspecialized peccoran stock, which accordingly precludes 

 a direct ancestorship to the Cervidse as a whole, because the American 

 genus is contemporary with more advanced peccoran forms of the Old 

 World. On the other hand, the Oligocene genus of America is regarded 

 as in line with Blastomeryx from the Miocene of the same general region. 

 The latter genus is in turn placed in the line of the recent American deer 

 [Mazama and Odocoileus). If we carry the line from Leptomeryx back 

 a step to the Eocene form Caniclomeryx (Scott, 1899, pages 67-73), or 

 some other contemporaneous genus, we would have the cer^^ids practically 

 as complete as any known phyletic series of the mammalia. 



Much material of the characteristic North American family Agrio- 

 choeridge has been accumulated the past ten years. The American Mu- 

 seum of Natural History and the Carnegie Museum especially have been 

 active in securing material of this family. No less than eight genera, 

 forty or more new species and subspecies, have been proposed (see Doug- 

 lass, Matthew, and Peterson), which further indicate the great variety of 

 forms when the large number already established is considered. That 

 this great branch of the American Tertiary artiodactyls was, during its 

 existence, capable of acquiring a variety of characters, which in some 

 respects are equal to or even greater than those of the Tylopoda or any 

 other branch of the Artiodactyla is evident, but why we should have no 

 recent representatives, while the tylopods, the deer, and. the peccaries 

 survived, is in reality as yet little understood, though we do hold the 

 opinion that one of the chief causes of their extinction is due to in- 

 adaptive combinations of characters. The family Agriochoeridae is very 

 much in need of a revision. 



Material of the fossil camels has been assembled in recent years, which 

 has resulted in a number of taxonomic changes of this important family. 

 As facts accumulate we are obliged to trim the phyletic trees and some- 

 times we meet with surprises entirely unlooked for. Among the more 

 recent surprises in this connection are perhaps the new genera Eotylopus 

 reedi (Matthew, 1910) from the Lower Oligocene of Wyoming and 

 Stenomylus (Peterson, 1906-1908) from the Lower Miocene of western 

 Nebraska. - The former genus is regarded as a primitive ancestor of the 

 Camelidse, found together with Pcehrotherium, a much more advanced 

 type, generally looked on as in the line to the recent camels, while the 

 latter is highly specialized in the dentition and many other features of 

 the cranium, plainly indicating a third line of early Tertiary origin 

 (Upper Eocene). The Stenomylins are already well known, there being 

 approximately one hundred or more individuals found, many of which 



