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seem to have the least claim to an alliance with the Mylodon on the score of the 

 organization of the fore-feet, which are reduced in one species to three digits, and 

 in the other to two ; the digits in both species being unique in their proportions 

 and rigidity of structure. How far real affinities may be masked under extreme 

 modifications of a fundamentally uniform type, a deeper insight into the struc- 

 ture of the carpus and metacarpus of these and other Edentata will clearly 

 show. 



With regard to the carpus of the Mylodon the coalescence of the scaphoides 

 and trapezium forms its chief characteristic. In the Myrmecophaga jubata, which, 

 in the proportions of the digits and in the shape of the ungual phalanges, and 

 more particularly in the want of this phalanx in the fifth digit, approximates 

 closer than the Manis to the Mylodon, the carpus, nevertheless, differs in struc- 

 ture in having the trapezium separate from the scaphoides, and in thus consist- 

 ing of eight distinct bones. Other differences present themselves in the propor- 

 tions and connections of the carpal bones : the lunare is articulated to both 

 ulna and radius ; the cuneiforme is separated by a wide interval from the fifth 

 metacarpal, which is articulated with an outwardly extended process of the un- 

 ciforme : the os pisiforme is here styliform, instead of being flattened into an 

 elliptical disc. 



In the Manis the carpus is reduced to seven bones, but it is by the same mo- 

 dification as in the Carnivora, viz. by the confluence of the scaphoides and lu- 

 nare : whilst the trapezium is free, of large size, and assists in supporting the 

 second metacarpal bone. The fifth metacarpal is here also separated from the 

 cuneiforme, and the pisiform bone is long and slender. 



In the Orycterope, although the thumb is reduced to a mere rudiment, the 

 trapezium exists independently, and not as a process of the scaphoides : the me- 

 dius digit no longer presents the characteristic magnitude which forms the con- 

 spicuous feature of the hand in the Ant-eaters and Mylodon ; the proximal end 

 of the middle metacarpal is contracted, not expanded ; the terminal phalanges 

 are not characterized by osseous claw-sheaths ; yet it is interesting to notice in 

 this remarkable quadruped, that the fifth metacarpal articulates with both unci- 

 form and cuneiform bones, as in the Mylodon. 



In the Armadillos the scaphoides and trapezium are distinct bones. Some 

 species are tetradactyle, like the Orycterope, but the normal number of digits is 



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