Article XVII. — AMERICAN EOCENE PRIMATES, AND 

 THE SUPPOSED RODENT FAMILY MIXODECTID^. 



By Henry Fairfield Osborn. 



The only American Primates at present known are those in 

 the Eocene. The supposed OHgocene Primates, Laopithecus 

 Marsh and Mcnotheriuni Cope, have proved to be identical 

 with Leptochcerus Leidy, an Artiodactyl. 



Invariably associated with the discovery and literature of 

 the Primates is the family Mixodectidee, including Mixodectes 

 and possibly Indrodon, Cynodontomys , and Mtcrosyops, now 

 supposed to be very primitive Rodents. In the writings of 

 Cope, Marsh, and Leidy, the bibliographical relations of these 

 two groups are so intimate that it is convenient to revise 

 them together. 



Altogether fifty-one species have been named, many of 

 them based upon defective types; the synonymy is truly 

 appalling, as shown in the chronological table. 



Many years ago I devoted several months to S3^stematic 

 revision as the basis of the present paper, examining and 

 comparing the types in the collections made by Leidy, Marsh, 

 and Cope, now in the Philadelphia Academy (Ph.), Ameri- 

 can Museum (A. M.) and Yale University (Y.). Unfortu- 

 nately all the types described by Cope for the Wheeler 

 Survey, and figured in his ' Extinct Vertebrata of New Mexico' 

 of 1874 have disappeared. A beginning is made here by 

 pointing out the synonymous genera but the species require 

 prolonged and microscopic examination and comparison. 

 This, however, is intended to supersede and replace all 

 previous revisions by the author and his staff in the 

 Museum. 



Dr. W. D. Matthew has rendered invaluable aid and advice 

 both in the morphological and descriptive part. In putting 

 together these notes and tables I have also been greatly 

 assisted by Mr. W. K. Gregory. The drawings are chiefly 

 the work of Mr. Weber, Mr. Horsfall, and Mr. Anderson. 



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