4) One reason for the multitude of names given to Notharctus was the frantic naming competition between O.C. Marsh and E. D. Cope. Another, however is the fragmentary nature of the fossils themselves. They commonly consisted of isolated teeth or small jaw fragments. Indeed, Leidy himself identified several other primate teeth and bone fragments as belonging to insectivores (the group of primative mammals most closely to primates) or to "pachyderms".
It should also be noted that the only bones shown in the article are a lower jaw of Notharcus (or rather reputed to belong to Notharcus) from a lithograph.