xvi.] PRIMATES. 285 



rounded ulnar sesamoid (the pisiform bone, /) which articu- 

 lates by a smooth facet with the cuneiform, but no radial 

 sesamoid. The trapezium (////) has a saddle-like articular 

 surface for the movable first metacarpal. The magnum 

 (m\ as its name implies, is the largest bone rather an 

 exceptional condition among Mammals ; it has a large 

 rounded part or head projecting upwards and fitting into a 

 concavity in the distal surface of the bones of the proximal 

 row. The unciform (u) has a strong hook-like process 

 from its palmar surface curved towards the radial side. 



The first metacarpal is shorter, though somewhat broader 

 than any of the others. It is articulated in a different plane 

 from them, its palmar surface facing towards the ulnar side 

 of the hand, and it is capable of a considerable range or 

 movement. The other four metacarpals are nearly equally 

 developed, diminishing slightly from the radial to the ulnar 

 side ; their shafts are slender and rather compressed, 

 especially towards the palmar aspect ; but they enlarge at 

 each extremity, particularly at the rounded distal end or 

 head. They are so articulated with the carpus as to allow 

 of very little motion. The phalanges are of the normal 

 number to each digit, all broad, convex on their dorsal, and 

 flattened or slightly hollowed on their palmar, side. The 

 proximal is the largest, and the ungual the smallest. The 

 latter is flattened and slightly expanded or spatulate at its 

 terminal portion. Those of the first, digit or thumb are 

 stouter than any of the others, those of the fifth digit (little 

 finger) are the most slender. The third digit is the longest, 

 the second and fourth somewhat shorter and nearly equal , 

 the fifth considerably shorter, and the first still more so. 

 Sesamoid bones are only developed below the metacarpo 

 phalangeal joint of the pollex. 



In the other PRIMATES, the manus is generally longer an 



