364 Woriman —Studies of Eocene Mammalia in the 



cusp of the heel, as in Microsyops. Associated with one of 

 the specimens containing the last lower molar is a portion of 

 an upper molar. Enough is preserved to show that there were 

 three main cusps, together with a rudimentary fourth, very 

 much as in Microsyops. 



The type specimen was found by Professor Marsh, at Grizzly 

 Buttes, Bridger Basin, on September 5, 1870; other specimens 

 were obtained at the same locality. 



The Relationship of the Microsyopsidm. 



There is as yet no absolutely conchisive evidence by means 

 of wliich the position of this group can be determined with 

 certainty. The species had always been considered, without 

 good reason, to belong to the Primates, until Matthew, from 

 an associated astragalus of Mixodectes pungens^ put forth the 

 view that these forms are rodents. Osborn following Matthew, 

 placed them in a primitive suborder of the Rodentia, which he 

 called Proglires. He says:"^ ''^Relationship to the Rodentia 

 is now found to be indicated by : (1) progressive elongation of 

 median incisor ; (2) disappearance of lateral incisor ; (3) reduc- 

 tion of canines ; (4) disappearance of the anterior premolars 

 and reduction of third premolar ; (5) transformation of fourth 

 premolar into molar forms, thus foreshadowing a homodont 

 molar-premolar series ; (6) ^vidth and extension of talonid (as in 

 Eocene Raramys)\ (7) rodent form of astragalus. Against 

 the Rodent relationship are : (1) Persistence of the canine ; 

 (2) absence of diastema ; (3) absence of any evidence (except 

 the levelling of the premolars) of adaptation for antero- 

 posterior or orthal motion of the jaw." 



If the astragalus which Matthew associates with the lower 

 jaw of Mixodectes really pertains to the same animal, there is 

 then strong presumptive proof that this species, at least, is not 

 a Primate. From long personal experience in collecting in the 

 Torrejon beds, however, I have found that only too frequently 

 the fossils are washed out of their original matrix and badly 

 mixed. Without a full knowledge of the circumstances under 

 which these particular specimens occurred, and in the absence 

 of reasonably conclusive evidence which w^ould tend to pre- 

 clude the possibility of a mixture, I should not feel inclined to 

 attach any very great weight to this association. At all 

 events, I should wish some stronger evidence upon which to 

 rest so important a generalization. As for Osborn's alleged 

 additional evidence of relationship to the Podentia, attention 

 may be called to the fact that he seems to have overlooked 

 Cheiromys and left it out of account entirely. With the 



* American Eocene Primates, etc., Bull. Amer. Miis. Nat. Hist., 1902, p. 

 204. 



