THE SKELETON OF THE TURTLE. ANTERIOR LIMB. 233 



The fore- arm includes two bones, the radius and ulna; 

 both these are small bones, and are immovably fixed to one 

 another proximally and distally. 



The radius or pre-axial bone is the larger of the two, and 

 is a rod-like bone terminated at either end by an epiphysis. 

 It articulates at its proximal end with the humerus, and at 

 its distal end with the radiale or scaphoid bone of the carpus. 



The ulna (fig. 40, A, 3) or post-axial bone is shorter than 

 the radius, and more expanded at its proximal end, where it 

 articulates with the humerus. It articulates distally with the 

 intermedium (lunar) and the ulnare (cuneiform) bones of the 

 carpus. All three bones of the arm have their terminations 

 formed by epiphyses which ossify from centres distinct from 

 those forming the shafts. 



The Manus consists of the carpus or wrist and the hand 

 which includes the metacarpals and phalanges. 



The carpus consists of a series of ten small bones, one of 

 which, the pisiform (fig. 40, A, 10), differs from the others in 

 being merely an ossification in the tendon of a muscle. The 

 remaining nine bones are arranged in a proximal row of three, 

 the ulnare (fig. 40, A, 6), intermedium, and radiale, and a 

 distal row of five (carpalia 1 5), each of which supports one 

 of the metacarpals. A ninth bone, the centrale (fig. 40, A, 7), 

 is wedged in between the two rows. The ulnare, intermedium 

 and pisiform are comparatively large flattened bones, the others 

 are small and cubical. 



The hand. This is composed of five digits, each of which 

 consists of a metacarpal and of a varying number of phalanges. 



The metacarpals. The first metacarpal (fig. 40, A, 11) 

 is a short flattened bone, the others are all elongated and 

 cylindrical, and are terminated proximally by slightly concave 

 surfaces, and distally by slightly convex ones. 



The phalanges. The first and fifth digits both have two 

 phalanges, the second, third, and fourth have each three. The 

 distal phalanx of the first digit is stout and curved, and bears 



