172 



worn down, as in the foregoing specimen, occasion the complex disposi- 

 tion of the thick enamel which is displayed in that specimen. 

 From the recent tertiary formations at Tarija, Upper Peru. 



Purchased. 



707. A fragment of the right ramus of the upper jaw with the base of a molar 



tooth of the Mastodon Andium, Humboldt. 



From the recent tertiary formations at Tarija, Upper Peru. 



Purchased. 



708. The proximal half of the right femur of the Mastodon Andium, Hum- 



boldt. It differs from that of the Mastodon giganteus in the greater 

 relative development of the trochanter major, which rises higher and 

 projects further outwards : this occasions a more concave outline of the 

 external border of the upper half of the femur in the Mastodon Andium : 

 the anterior surface of the bone likewise slopes more towards that border, 

 and the posterior surface of the upper part of the femur is flatter in the 

 Mastodon Andium than in the Mast, giganteus. 



From the recent tertiary deposits at Tarija, Upper Peru. 



Purchased. 



709. The distal end of the left femur of the Mastodon Andium (?). It differs 

 from the corresponding part of the Mast, giganteus in the more angular 

 depression for the patella, in the greater length of the rotular surface in 

 proportion to its breadth, and in the well-marked ridge by which that 

 surface overhangs, or is divided from, the inter-condyloid depression ; 

 this depression, also, is relatively wider than in the Mast, giganteus. 



From the tertiary deposits in the province of Buenos Ayres. 



Presented by Charles Darwin, Esq., F.R.&. 



710. The distal half of the right tibia, broken lengthwise, of the Mastodon 



Andium, Humboldt. 



From the recent tertiary deposits at Tarija, Upper Peru. 



Purchased. 



Mastodon giganteus. 

 Growth and Succession of the Teeth. 



711. A portion of the upper jaw of a young Mastodon giganteus, Cuv., with 



