xvi.] MONOTREMATA. 311 



consists of a scapho-lunar and a cuneiform. There is no 

 central. The dibtal row has the usual four bones. The 

 pisiform is large, and articulates with the ulna as well as the 

 cuneiform, and there is a small radial sesamoid, articulating 

 with the scapho-lunar. There are also two large sesamoids, 

 sometimes united, in the palmar tendons. The digits are 

 five in number, all with the normal number of phalanges, 

 which are short and broad, except those that bear the 

 long, slightly curved, broad nails, with which the animal 

 scratches and burrows in the ground. The pollex is more 

 slender than the other digits ; it is of about the same length 

 as the fifth, the second and fourth are nearly equal and 

 longer, and the third slightly the longest. 



In the Ornithorh)nchus the manus is comparatively more 

 slender and elongated ; but the number and arrangement 

 ot the bones are the same as in the Echidna. 



