372 Bulletin American Museum of Natural History. [Vol. XXVII, 



Ord. Condylarthra. Fam. Plienacodontidae [Didolodus, Notoprotogonia, 

 Lambdaconus, etc.], Periptychidae [Argyrolambda, Josepholeidya, etc.], 

 Pantolambdidae [Ricardolydekkeria, Guiliehnofloweria, etc.] 



Ord. Perissodactyla. Fam. Hyracotheiiidae [Hyracotherium, Ectocion, 

 Proectocion, etc.], Palaeotheriidae [Palaeotheriuiii, Pajoplotherluni, 

 Victorlemoineia, Anchitherium, Parahippus, Hypohippus, etc.], Pro- 

 terotheriidae [Proterotherium, Thoatherium, Diadiapliorus etc.], Ma- 

 crauchenidae [Theosodon, Scalabrinitherium, Macrauchenia etc.], 

 Rhinoceridae, Tapiridae. 



Ord. Artiodactyla. Fam. Suidae, Camelidae, Cervidae, Bovidae. 



Ord. Proboscidea. Fam. Garolozittelidae, Pyrotheriidae. 



Ord. Amblypoda. Fam. Pantostylopidac [Pantostylops, Hemistylops etc.] 

 Trigonostylopidae [Trigonostylops etc.], Albertogaudryidae [Alberto- 

 gaudrya etc.] Coryphodontidae [Coryphodon], Astrapotheriidae [Astra- 

 potherium, Astrapothericulus, Astraponotus, etc.], Uintatheriidae 

 [Uintatherium]. 



Ord. Ancylopoda. Fam. Isotemnidae [Isotemnus, Pleurostylodon etc.], 

 Leontiniidae [Leontinia, Colpodon etc.], Homalodontotheriidae [Hom- 

 alodotherium, Asmodeus etc.]. 



Ord. Tillodonta. Fam. Notostylopidae [Notostylops etc.], Tillotheriidae 

 [Tillotherium], Exthonychidae [Exthonyx]. 



It is only gradually coining to be realized that parallel and convergent 

 evolution have been largely influential in bringing about resemblances in the 

 dentition and skeleton between the extinct South American hoofed mammals 

 and those of the northern world. As shown in the classification quoted 

 above Ameghino refers the Archteohyracidae to the Hyracoidea, the Noto- 

 hippidje to the "Hippoidea," the Proterotheriida? and Macrauchenidse to 

 the Perissodactyla, the Astrapotheriidae to the Amblypoda etc. But the 

 investigations of Lydekker, Roth, Gaudry (1906-1909), Scott, Sinclair 

 and others have made it appear very probable : first that the extinct South 

 American hoofed mammals belonged to peculiar southern groups which 

 followed their own lines of evolution independently of the mammals of the 

 rest of the world; secondly that in becoming adapted to a herbivorous diet 

 they often "paralleled" the northern ungulates in many characters; thirdly 

 that such adaptive characters are never associated in exactly the same com- 

 binations in northern and southern groups. 



The memoirs by Professor Scott and Dr. Sinclair, now in progress, on 

 the material collected by Hatcher in the Santa Cruz ( ?]Miocene) beds, may 

 be expected to deal definitively with many of the systematic and genetic 

 problems of the South American imgulates; but meanwhile, for the purposes 



