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



[Suborder] Perissodactyla. Fam. Equidae, Proterotheridae, Ma- 



crauchenidae, Tapiridae, Rhinoceridae, Titanotheridae, Chalico- 



theridae. 

 1893. Lydekker. 

 Order Ungulata. 



Suborder Toxodontia. Fam. Pachyrucida?, Typotheriidte, Toxo- 



dontidcie. 

 Suborder Astrapotheria [subord. nov.] Fam. Homalodontotheriidse, 



Fam. Astrapotheriidse. 

 Suborder Litopterna. Fam. Proterotheriidse, Fam. Macrauche- 



niidse. 



"... . phylogenetically the Toxodonts may apparently be regarded as related 

 to the Peris.sodactyla, but a.s retaining certain features now common to the 

 Artiodactyla which have probably been inherited from common Condylarth- 

 rous ancestors. The structure of the carpus precludes the inclusion of the 

 group in the Subungulata, among which it has been placed [by Flower and 

 Lydekker] and indicates that the Toxodonts must occupy a position of equal 

 rank with the Artiodactyla and Perissodactyla. ..." (p. 3). 



As regards the Litopterna the author states (j). 56) that the group "ap- 

 pears to hold a somewhat intermediate position between the Astrapotheria 

 and the Perissodactyla, although the peculiar character of the cervical 

 vertebrae indicate that it cannot in any way be regarded as ancestral to the 

 latter suborder." 



1903. Roth. 

 [Order Ungulata.] 



[Suborder] " Notoungulata (los generos Toxodon, Nesodon y Typothe- 



rium) los tipos del grupo Notoungulata muestran una particularidad 



en la construccion de los huesos temporales que no existe en ningun otro 

 suborden de los Ungulados." The author here refers to the peculiar con- 

 struction of the temporal region in the above mentioned group and speaks 

 of it as "un caracter tipico y constante, como lo es, por ejemplo, el angulo 

 mandibular invertido en los Marsui)iales . . . . " Consequently the author 

 meant to exclude from this group the Astrapotheres and Litopterns, which 

 are said to lack this character. 



1904. Scott. 

 Notoungulata. 

 L Toxodontia. 



1 . Toxodonta. 



2. Typotheria. 



3. Homalodotheria. 



