SKELETON€6WTlMOlf^W|f^E*5«|A. 325 



; NEwyqefc ' . J. 



same transverse line. Th4'^^,ypraaial .ii^l^^jfities receive the two 

 articular convexities of tlie broifai^^^^j^^ffiiar bone, fig. 206, « ; 

 the two convex trochleas of the ulna play upon two concavities, 

 one-half of each of w^hich is contributed by the cuneiform, ib. h, 

 and pisiform, c. This complicated joint limits the movement of 

 the hand upon the fore-arm to flexion and extension. 



Notwithstanding the confluence of the scaphoid with the lunar 

 bone in the carpus of the Echidna, as in that of the Marsupials 

 and Carnivora, it includes eight ossicles, a small sesamoid bone, 

 ^g. 206, X, being developed in the tendon of the flexor carpi 

 radialis, and articulated with the scapholunar bone, a, and 

 radius. The distal series of the carpus includes the four nor- 



206 



207 



Bones and claws of the fore-foot. Echidna, anconal aspect. 



Bones of the fore-foot. 

 Echidna, palmar aspect. 



mal bones, the trapezium, ib. d, supporting the innermost digit 

 or pollex, the trapezoides, e, the index, the os magnum, f, which 

 is almost the smallest, sustaining the medius, and the unci- 

 forme, g, the two outer digits : in the Ornithorhynchus the os 

 magnum contributes a greater share to the articulation w4th the 

 rino;-fino:er. 



In the Echidna all the bones of the fore-extremity are rela- 

 tively larger and stronger than in the Ornithorhynchus, but this 

 diiFerence is especially remarkable in the metacarpals and two 

 first rows of phalanges, fig. 206, h, i, k, which are singularly 

 short, broad, and thick. The palm is strengthened by two large 

 sesamoids developed in the flexor tendons; these are sometimes 



