1910.] Taxonomic History of the Ungulata. 353 



TI. Ordn. Artiodactyla. 



A. Noiiruminantia. 



1. T"iiteiordn. Suoidea. Hippopotaniidae, Suidae, 

 Elotheriidae. 



B. Ruminantia. 



2. ITnterordn. Tylopoda. C'aiiielitlae, Oreodontidae, 

 Hoinacodontidae. 



3. I"nterordii. Pecora. Cervidae, Bovidae, Giraffidae. 



4. ITnterordn. Traguloidea. Tragulidae. 



5. Unterordn. Dichobunoidea. Auoplotheriidae, Dich- 

 obimidae (Subfani. Xiphodontinae, Caenotheriinae). 



6. ITnterordn. Anthracotheroidea. Anthracotherii- 

 dae. 



III. Ordn. Condylarthra. Phenacodontidae, Meniscotheriidae, 



Mioclaenidae. 

 IV. Ordn. Ancylopoda. Chalicotheriidae, ? Homalodonto- 



theriidae. 

 V. Ordn. Litopterna. Proterotheriidae, Macrauchenidae, ? 



Astrapotheriidae. 

 VI. Ordn. Amblypoda. 



1. Subordn. Taligrada (Cope) Osborn. Periptychidae, 

 Pantolambdidae. 



2. Subordn. Pantodonta Cope. Coryphodontidae. 



3. Subordn. Dinocerata Marsh. 



VII. Ordn. Toxotlontia. Typotheriidae, Toxodontidae, Proty- 



potheriidae, Hegetotheriidae. 

 VIII. Ordn. Hyracoidea. 

 IX. Ordn. Proboscidea. Dinotheriidae, Elephantidae. 



This classification is wisely conservative in spirit but is probably sus- 

 ceptible of improvement in the following details: 



(1) The group Diplarthra is very likely unnatural, even in a super- 

 ordinal sense (p. 400). 



(2) The Ancylopoda are probably closely related to the Perissodactyla 

 and not related to Homalodoniotherium (pp. 397, 399). 



(3) The Anthracotheroidea are probably related more nearly to the 

 Suina than to the Ruminantia. 



(4) The Litopterna are probably related superordinally to the Toxo- 

 dontia (p. 378). 



The classification adopted in the present work is given on pages 464-466. 



