106 



having the cornua shorter, straighter, more prismatic, and the sides 

 flatter and meeting at sharper edges, especially at the upper part : the 

 articular surfaces for the thyroid cornua are at the posterior instead of the 

 under surface of the expanded end of the cornua. The articular surfaces 

 for the anterior cornua are upon the anterior part of the angles of the 

 body, not raised upon tuberosities : the ceratohyals were perhaps articu- 

 lated by the intervention of a short bony piece, which, anchylosed to the 

 body in the Mylodon, may give rise to the characteristic tubercles of the 

 bone in that genus. The body of the hyoid, in the present specimen, 

 presents two convex ridges below the articular surfaces, and is flattened 

 and slightly expanded at the under part. 



From the tertiary deposits at Buenos Ayres. Purchased. 



511. The left stylo-hyal bone of a large Megatherioid quadruped. 



From the tertiary deposits of Buenos Ayres. Purchased. 



512. The sternal extremities of the two clavicles of a Mylodon or of a Mega- 



lonyx. 



From the tertiary deposits of Buenos Ayres. Purchased. 



513. The distal half of the right femur of a Megatherioid animal of the size of 



the Mylodon or Megalonyx ; it resembles the same bone of the Mylodon 

 in its great breadth and antero-posterior compression, but differs in 

 being excavated by a medullary cavity, and in having the rotular articular 

 surface distinct from those of the two condyles : in the latter structure 

 it resembles the Megalonyx, but differs from the Megalonyx Jeffersoni 

 in the general form of the articular surface. 



From the tertiary deposits of Buenos Ayres. Purchased. 



514. The right astragalus of a Megatherioid quadruped, somewhat larger than 

 the Mylodon robustus : it resembles the astragalus of the Mylodon in 

 the flattening of the upper half of the navicular surface, but differs in 

 having the calcaneal surface divided into two parts by a deep rough 

 groove, in which character it resembles the Megatherium. 



From the tertiary deposits of Buenos Ayres. Purchased. 



