148 Eaton — Vertebrate Fossils from Ayusbamba, Peru. 



molar : for the first cross cusp 7'3 cra , for the 2nd 7'± cm , for the 

 3rd 7*2 cm . Taking into consideration the characters of this 

 molar tooth and also those of the fragment of tusk, previously 

 described, I am confident that both of these specimens should 

 be ref erred to Mastodon bolivianus, or Dibelodon bolivianus, 

 if it is best to use the generic name proposed by Cope. 



It is not surprising that remains of this species should be 

 found at Ayusbamba, for Ulloma, where the type material of 

 D. bolivianus was obtained, is less than 350 miles distant, 

 being situated at an altitude of about 3,800 meters, in the high 

 Bolivian table-land south of Lake Titicaca. There seems to 

 be no reason to doubt that the same climatic conditions pre- 

 vailed in these two localities during the early Pleistocene. 



Mylodon sp. 



The Gravigrade Edentates hold such an important place in 

 the Pleistocene fauna of South America, and have been so 

 closely associated, in their distribution, with the Elephantidte 

 and Equidre, that one might expect to find the group repre- 

 sented in the collection from Ayusbamba. Vertebrae, pieces 

 of the ribs, including an ossified sternal section with its charac- 

 teristic double articulation, and an ungual phalanx, from this 

 locality, should be referred provisionally to the genus Mylodon, 

 so closely do they resemble the corresponding parts of the 

 mounted skeletons of M. robustus and M. myloides in the 

 American Museum of Natural History. I have no means of 

 determining the species. In this connection may be men- 

 tioned a humerus of Mylodon that was found, not at Ayus- 

 bamba, but within two miles of Cuzco. where the road to 

 Ayusbamba ascends from the Huancaro Valle} r . The location 

 of the bone beneath well-defined beds of fine and coarse allu- 

 vium, about 28 feet in thickness, is marked in text-figure 4 

 by the point of an arrow. This humerus, shown in Plate V, 

 figures 5 and 6, differs from the humeri of M. robustus and 

 M. myloides at the American Museum in not having so 

 prominent a deltoidal tract. The outer tuberosity is also 

 smaller, and the posterior outline, immediately below the head, 

 is more deeply concave. These differences, while slight, are 

 sufficient to indicate that some species of Mylodon other than 

 M. robustus and M. 'myloides occurred in this part of the 

 Cordillera. Potsherds and bones of llamas were observed at a 

 depth of 2£ feet in the surface stratum at the top of the bank 

 where this humerus was found ; but no objects were seen in 

 the lower strata that could, in any way, associate the Mylodon 

 bone with the period of human inhabitation. 



