1910.] Recent Classifications of South American " Ungulates." 371 



II. Litoptema [misprint for Litopteriia]. 



III. ? Astrapotheria. 



The author states that although the Litopterna and Astrapotheria lacic 

 the peeuHar structure of the periotic region referred to by Roth, yet on the 

 other hand "all of the orders, including at least the Litoptema [Litopterna], 

 have certain constant characteristics, such as the extensive articulation 

 between the fibula and calcaneum, the convex distal end of the astragalus, 

 which does not rest upon the enboid, and some peculiarities in the form of 

 the teeth. The limb and foot bones of the Astrapothina [Astrapotheria] 

 are not yet known, and their systematic position is, therefore, still a matter 

 of conjecture. There is a striking similarity between the dentition of these 

 animals and that of the northern genera, Cadureotherium [Cadurcotheriwn] 

 and Metamnnodon, but the form of the skull is so radically different as to 

 make it probable that the resemblance in dentition is analogical only. 



"It seems likely, therefore, that Hoth's term, 'Notoungulata' may 

 properly be extended to include all of the Santa Cruz hoofed animals, and 

 that all of the groups which agree in the structure of the periotic region, 

 already alluded to, should be regarded as sub-orders of the Toxodontia. 

 This conception is shown in the following provisional table [given above] .... 

 "While these South American imgulates are singularly different frona those 

 of the Northern Hemisphere, it does not seem at all likely that they origi- 

 nated altogether independently of the latter. x\meghino has described a 

 number of genera from pre-Patagonian formations which, though incom- 

 pletely known, appear to be referable to the Condylarthra, the parent stock 

 of the northern Ungulates. Very probal)ly an early Eocene or late Mesozoic 

 migration brought the Condylarthra into South x\merica, and there, in 

 almost complete isolation, they gradually gave rise to the various peculiar 

 orders and suborders of the Notoungulata. The possibility of such migra- 

 tion is shown by the discovery of an armadillo in the Middle Eocene of 

 North America" {op. cit., p. 590). 

 1904. Ameghino. In the "Liste des Figures distribuees i)ar Ordres et 



par Eamilles" (p. 511) the following arrangement is adopted: 

 Ord. Protungulata. Fam. Caroloameghinidae [ ?Polyproto(lont Marsu- 

 pials]. 

 Ord. Lemuroidea. Fam. Archaeopithecidae, Notopithecidae, Henricosbor- 



nidae, Adapidae, Microchceridae. 

 Ord. Simioidea. Fam. Homunculidae, Cebidae, Cercopithecidse, Simiidae. 

 Ord. Hyracoidea. Fam. x\coelodidae, Archaeohyracidae, Adiantidae. 

 ( )rd. Typotheria. Fam. Protypotheriidae, Hegetotheriidae. 

 Ord. Toxodontia. Fam. Nesodontidae, Toxodontidae. 

 Ord. Hippoidea. Fam. Notohippidae, Equidae. 



