63 



pebbles cemented together by calcareous matter, so that only the upper 

 or alveolar border is visible. The coronoid and condyloid processes are 

 broken away, and the texture of the remaining part of the jaw is too 

 friable, and adheres too firmly to the surrounding matrix, to admit of more 

 of its form being ascertained. 



There were four molars on each side of this jaw ; the large oblique 

 perforation near the fractured simphysis is the anterior extremity of the 

 wide dental canal. The forms of the alveoli are best preserved in the 

 right ramus ; the first is the smallest and seems to have contained a 

 tooth, of which the transverse section must have been simply elliptical : 

 the second tooth is preserved in situ ; it is laterally compressed, but the 

 transverse section is ovate, the great end being turned forwards : the 

 third socket presents a corresponding form, but a larger size : the fourth 

 socket is too much mutilated to allow of a correct opinion being formed 

 as to the shape of the tooth which it once contained. 



From the Cliffs at Punta Alta, Bahia Blanca, near Patagonia. 



Presented by Charles Dartviii, Esq., F.R.S. 



Genus Mylodon. 



377- The skeleton of the Mylodon robustus, Owen. 



This skeleton was discovered in the year 1841, by M. Pedro de Angelis, 

 seven leagues north of the city of Buenos Ayres, in the fluviatile deposits 

 constituting the extensive plain intersected by the great Rio Plata and its 

 tributaries. 



It is remarkable for the great strength which is indicated by its robust 

 proportions, and by the powerful development of the ridges and by pro- 

 cesses for the attachment of muscles. 



The trunk, which is shorter than that of the Hippopotamus, is ter- 

 minated behind by a pelvis, equalling in breadth and exceeding in depth 

 that of the Elephant. This capacious bony basin rests on two massive 

 but short hind extremities, terminated by feet as long as the femora, 

 set at right angles to the leg, as in the plantigrade animals, but with the 



