18 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.63. 



rally be expected that many of the early Eocene and Paleocene 

 representatives of the Primates would have just such a type of foot ? 



OBSERVATIONS ON THE EVOLUTIONARY STAGE AND SYSTEMATIC 

 POSITION OF THE EARLY TERTIARY PRIMATES. 



While great process has been made in recent years in our under- 

 standing of tooth structure, giving more confidence in its use, it is 

 fully appreciated as already acknowledged, that there are many 

 difficulties and hazards to be encountered in attempting, on dental 

 characters alone, criticisms of or deviations from widely accepted 

 opinions. However, this brief restudy undertaken from the angle of 

 an earlier phase has deeply impressed the present writer with 

 the suggestion that certain widely accepted views regarding the 

 Eocene Primates should be very considerably modified to come in 

 agreement with our increasing knowledge of facts, acquired though 

 it be for the greater part through the study of dental characters; 

 for notwithstanding the greatly augmented collections of the past 20 

 years, it is on the study of those characters, for the most part, that 

 we must still rely for our information regarding the greater number 

 of species of the early Tertiary. 



Owing to this treacherous resemblance of tooth structure in en- 

 tirely unrelated forms (a fact long recognized) there existed, up to 

 the time of the discovery of skull and skeleton portions which gave 

 some knowledge of other anatomical characters, the widest differences 

 of opinion regarding the proper ordinal position of the earlier de- 

 scribed Eocene Primates. For example, when Notharctus, which was 

 founded on a lower jaw, was described by Leidy in 1870, it was not 

 definitely referred to any existing order of mammals, Leidy consider- 

 ing that it carried resemblances in tooth structure to both the Car- 

 nivora and to certain Eocene "pachyderms." The next year (1871) 

 Marsh Hkewise described a similar lower jaw fragment, noting re- 

 semblances to a contemporaneous genus Hyopsodus, a supposed suil- 

 line. Cope, for some time misled by a false association of creodont 

 ungual phalanges with teeth belonging to a species of the Notharctus 

 group, failed to recognize the full primate affinities of the Notharctids 

 and placed them with a rather heterogeneous group of genera under 

 a new suborder, Mesodonta, which he considered as holding about 

 the same relationship to the Primates as the Creodonta to the Car- 

 nivora. Later, each of these authorities recognized true Primate 

 characteristics in this group as well as the contemporaneous "Anato- 

 morphous" group, but got little further than that in their classification. 



This illustrates well the rather chaotic condition of our knowledge 

 of the early North American Primates up to the time of their first 

 revision by Osborn in 1902,^" and also emphasizes the difficulties en- 



"BuU. Amer. Mus. Nat- Hist., vol. 16, art. 17 1902,, pp. 169-241. 



