Marsh Collection, Peabody Museum. 409 



he does not state this directly. He defined the Mesodonta as 

 follows : " Incisors not growing from persistent pulps ; molars 

 tubercular, never sectorial ; third trochanter elevated ; astragalus 

 not grooved above. " Under the head of Prosimige, he further 

 adds, " The suborder may be differentiated from the Mesodonta 

 by the possession of an opposable hallux of the posterior foot, " 

 but qualifies this definition with the statement that the lack of 

 opposability of the hallux is not demonstrated in any of the 

 species except Pelycoclus. 



There seems to be a great deal of confusion in Cope's state- 

 ments regarding the classification of the genera under the 

 Mesodonta and Prosimige. In the Mesodonta, he classified the 

 following genera : Omomys, Microsyops, Pantolestes, Tom- 

 itherium, Pelycoclus, Sarcolemur, Pyopsodus, Aphelions, 

 Aclapis, and Opisthotonus. In the Prosimige, on the other 

 hand, he included three families, viz. ; Adapidae ( genera not 

 stated ), Mixodecticlge comprising the genera Mixodectes, 

 Microsyops, and Cynodontomys, and the Anaptomorphidge 

 including Anaptomoiphus and Necrolemur. It will be thus 

 seen that several of the generate referred to both suborders. 



The next authority of note to contribute to this subject is 

 Schlosser. He regarded all these early extinct forms as con- 

 stituting a group equal in rank to that of the Lemuroidea and 

 Anthropoidea, and one from which these two, in all probabil- 

 ity, have been derived. This group he named the Pseudole- 

 muroidea. Osborn in his recent paper, " American Eocene Pri- 

 mates, "* inclines apparently to the same view. He says: 

 " Three suppositions are possible : First, that these Primates 

 represent an ancient and generalized group ( Mesodonta, Cope ) 

 ancestral to both Lemuroidea and Anthropoidea ; second, 

 that they include representatives of both Lemuroidea and 

 Anthropoidea, contemporaneous and intermingled ; third, that 

 they belong exclusively to one or the other order. There are 

 certain advantages in the revival of the term Mesodonta Cope, 

 a suborder (anticipating the terms Pseudolemuroidea and 

 Tarsii) which would bear somewhat the same relationship to 

 the modern specialized Monkeys and Lemurs that the Condy- 

 larthra bear to the Ungulata and the Creodonta to the Carniv- 

 ora. " 



As regards the validity of the group Mesodonta of Cope and 

 its suggested revival by Osborn, very little need be said. 

 From the most abundant skeletal materials of both Adapts and 

 JSfotharctus we now know that the hallux was almost if not 

 quite as opposable as in any living Primate. Cope's statement, 

 therefore, of its lack of opposability in Pelycodus, a genus 

 scarcely distinct from Notharctus, must with almost absolute 



*Loc. cit. 



