88 Mr. Owen on the Glyptodon clavipes. 



m 



socket thirteen lines ; its transverse diameter cannot be determined, the inner wall 

 of the socket being broken away. 



Humerus. — The distal half of the left humerus exhibits a thick projection beyond 

 the internal condyle, and a broad, thin, and well-produced supinator ridge above 

 the external condyle, which, with the articular trochlea for the antibrachial bones, 

 are closely conformable with the structure of the humerus in the Armadillos ; but 

 the internal condyle is not perforated, and the depressions above the trochlea, 

 both in front, and more especially that behind, are relatively deeper. The twist of 

 the humerus is strongly marked; the base of the strong deltoid trochanter is discern- 

 ible at the fractured extremity of the bone ; but on the opposite side there is a rugged 

 raised surface for a muscular insertion, of which I do not perceive the analogue 

 in the Armadillos. The humerus of the Megatherium, notwithstanding it apparently 

 offers the same exception among Edentata with that of the Glyptodon in the im- 

 perforation of the internal condyle, differs widely from the present bone in the ex- 

 traordinary expansion of its distal extremity, especially of the external condyle. 



Radius. — The i-adius of the Glyptodon, in its comparative shortness and general 

 form, likewise corresponds very closely with that of the Armadillos ; it differs prin- 

 cipally in being less compressed. The proximal, semioval, articular surface, which 

 plays upon the anterior part of the trochlea of the humerus, is, in the transverse 

 direction, convex on the inner and concave on the outer side ; the inner part of 

 the proximal end is much produced : the posterior surface of the bone is traversed 

 longitudinally by a deep and wide rugged groove ; the bone assumes somewhat of 

 a trihedral figure towards its distal end ; the anterior ridge is produced below the 

 distal articulation in the form of an obtuse, sub-compressed process ; the posterior 

 ridge terminates in a broad rugged process ; the radial, which in the prone position 

 of the bone becomes the inner side of the distal extremity, is much produced ; 

 the distal articular concavity is formed by an oblique excavation leading down- 

 wards from the posterior towards the anterior margin of the distal end ; the 

 articular surface is divided by an oblique groove into two parts, and in some species 

 of Armadillo this groove is represented by an entering notch. 



The description and figure which Professor D'Alton has given of the radius, which 

 forms one of the series of bones associated with the bony armour described by 

 Professor Weiss, proves them to belong to a species of Glyptodon identical with 

 the present : the characteristic process from the fore-part of the distal end of the 

 radius appears, however, to be broken off in Sellow's specimen ; and the bone is 

 about one-fourth smaller, belonging, as the separate epiphyses demonstrate, to an 

 immature individual. The radius here described measures seven inches and a half 

 in length, and three inches across its distal end. 



The perfect radius of the Megatherium, forming part of the skeleton brought to 

 this country by Sir Woodbine Parish, fortunately affords the means of a close com- 



