8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



Meniscotherium was ancestral to the chalicotheres. In Ameghino's 

 arrangement the Homalodontotheriidae occupied this position with 

 respect to the chalicotheres of the boreal hemisphere, and the meni- 

 scotheres were described as allied with the Proterotheriidae with 

 which they must have had a common but as yet undiscovered ances- 

 try. This was later than Cope's (1891) observation that the denti- 

 tion of the Macraucheniidae could have been derived from that of the 

 Meniscotheriidae, as well as that the dentition of the Proterotheriidae 

 could easily be derived from that of the Periptychidae. In 1901 

 Ameghino went so far as to include within the family Meniscotherii- 

 dae various genera of litopterns now divided between the Protero- 

 theriidae and Macraucheniidae. In the meantime, Wortman (1896) 

 attributed the appearance of the Proterotheriidae to a southward mi- 

 gration of the meniscotheres and later (1904) enlarged upon this hy- 

 pothesis to postulate that not only were the Litopterna direct deriva- 

 tives of Meniscotherium but that all South American ungulates were 

 but modified descendents of North American condylarths. 



Cope's suggestion of a condylarthran relationship to the hyracoids, 

 which seems first mentioned in 1882(b) and later reflected in his 

 taxonomic arrangement (1884b), was early championed by Wortman 

 (1886). While Cope was concerned with certain resemblances in 

 the structure of feet, Wortman, in reviewing teeth of Meniscotherium, 

 saw a marked indication there of hyracoid affinity and was disposed 

 to regard this genus as the direct ancestor of the Hyracoidea. 



Marsh (1892) noted the Hyrax-like appearance of the carpals 

 and tarsals which he indicated in his name Hyracops but evidently 

 did not regard the relationship as close, as he proposed for the 

 meniscotheres the new ordinal name Mesodactyla and about which 

 he stated as follows : "The teeth are somewhat similar to those of 

 Ungulates, but the rest of the skeleton, especially the limbs and feet, 

 are of a generalized type quite distinct from any hoofed animals 

 known, recent or extinct. Some parts of the structure seem to 

 indicate an affinity with Jlyrax, but the limbs and feet show characters 

 resembling those of Primates, especially the extinct forms, and like- 

 wise seen in Insectivores, and even in some of the Rodents." 



A little later that year (1892) Scott, although not certain that 

 Meniscotherium was a direct ancestor of the modern hyracoids, was 

 convinced from Marsh's (1892) portrayal of the feet of "Hyracops" 

 and from his own study of meniscotheriid premolars that the family 

 should be removed from the Condylarthra and included in the 

 Hyracoidea. In 1913 Scott regarded this arrangment as improbable, 



