408 THE VERTEBRATE SKELETON. 



notch is called the coronoid process. Somewhat in front 

 of and below the sigmoid notch is a smaller hollow (fig. 77, 13), 

 with which the radius articulates. 



In the young animal the ends of both radius and ulna are 

 seen to ossify from centres different from those forming the 

 shafts. The epiphyses forming both ends of the radius, and the 

 distal end of the ulna are large, while that at the proximal end 

 of the ulna is small, and forms only the end of the olecranon. 



The Maims is divided into 



a. The carpus or wrist, formed of a group of small 

 bones. 



b. The hand, which includes firstly some elongated 

 bones, the metacarpals, forming what corresponds to the 

 palm of the hand, and secondly the phalanges, which form the 

 fingers. 



The Carpus or wrist. The carpus of the dog consists of 

 seven small bones, arranged in a proximal row of three, and 

 a distal row of four. It differs much from the simpler type 

 met with in the newt. The largest bone of the proximal row 

 is the scapho-lunar (fig. 80, 1), formed by the fused scaphoid 

 (radiale), lunar (intermedium), and centrale ; it has a large 

 convex proximal surface for articulation with the radius, and 

 articulates distally with the trapezium, trapezoid, and magnum, 

 and internally with the cuneiform. The cuneiform (ulnare) 

 (fig. 80, 2) has a posterior rounded surface articulating with 

 the ulna ; it articulates in front with the unciform, arid in- 

 ternally with the pisiform (fig. 80, 7), which is a compara- 

 tively large sesamoid bone on the ulnar side of the carpus. 

 Frequently also there is a small sesamoid* bone on the radial 

 side of the carpus. The trapezium (carpale 1), trapezoid 

 (carpale 2), and magnum (carpale 3) (fig. 80, 5) are all small 

 bones, and support respectively the first, second, and third 

 metacarpals. The unciform (carpalia 4 and 5) (fig. 80, 6) 

 is larger, and supports the fourth and fifth metacarpals. 



