354 ANATOMY OF VERTEBRATES, 



digit, and has a small sesamoid bone articulated to its radial 

 surface. The trapezoides is articulated to the index digit, and is 

 wedged between the scapholunar bone and os magnum ; this 

 forms an oblique articular surface for the middle digit ; but the 

 largest of the second series of carpal bones is the cuneiform, which 

 sends downward an obtuse rounded process, and receives the 

 articular surface of the fifth, and the outer half of that of the 

 fourth digit, the remainder of which abuts against the oblique 

 proximal extremity of the middle metatarsal bone. The five 

 metacarpal bones are all thick and short, but chiefly so the 

 outermost. The innermost digit, or pollex, has two phalanges, 

 the remainder three ; the ungual phalanx of all the digits is 

 conical, curved, convex above, expanded at the base, and simple 

 at the opposite extremity. In the Perameles the ungual phalanx 

 of the three middle dimts of the hand, and of the two outer dio-its 

 of the foot, are split at the extremity by a longitudinal fissure 

 commencing at the upper part of the base. This structure, which 

 characterises the ungual phalanges in the placental Anteaters, 

 has not been hitherto met with in other Marsupial genera.^ The 

 terminal phalanges of the Koala are large, much compressed 

 and curved ; the concave articular surface is not situated, as 

 in the Cats, on the lower part of the proximal end, but, as 

 in the Sloths, at the upper. The claws which they support are 

 long. 



In the Great Kangaroo the first row of the carpus is composed, 

 as in the Wombat, of three bones, but the apex of the ulna 

 rotates in a ca^dty formed exclusively by the cuneiforme. There 

 are four bones in the second row ; of which the unciform is by far 

 the largest, and supports a part of the middle, as well as the two 

 outer digits. In the Potoroos I find but three bones in the distal 

 series of the carpus, the trapezoides being wanting, and its place 

 in one species being occupied by the proximal end of the second 

 metacarpal bone, which articulates with the os magnum. In the 

 Perameles there are four bones in the second carpal row, although 

 the hand is less perfect in this than in any other Marsupial 

 genus, Chceropus excepted, the three middle toes only being fully 

 developed. In the Petaurus the carpus is chiefly remarkable for 

 the length of the pisiforme. 



It would be tedious to dwell on the minor diflerences observable 

 in the bony structure of the hand in other Marsupials. I shall 

 therefore only observe that though the inner digit is not situated 



' It would be instructive to examine tlie skeleton of the rare Chceropus, with 

 reference to this structure. 



