32 ANATOMY OF A CHELONIAN. 



plane, and, in its position of rest, with the humerus di- 

 rected forward and the forearm and manus backward ; 

 also that the two bones of the forearm lie in a dorso- 

 ventral plane, the ulna being dorsal. If the forelimb 

 w^ere stretched out so that its axis was perpendicular 

 to the median antero-posterior dorso-ventral plane of 

 the trunk the thumb side would be ventral. 



65. The humerus has a short, thick shaft with expanded 

 articular extremities. The proximal extremity, set on 

 to the shaft nearly at a right angle, has two very large 

 tuberosities, and articulates with the glenoid fossa. On 

 the distal end is the articular surface for radius and 

 ulna. 



66. The bo?ies of the forearm {radius and uhia) are sep- 

 arate and flattened, and somewhat constricted in their 

 median portions. The ulna is thicker and larger than 

 the radius, and reaches beyond it at the elbow ; at the 

 wrist, the reverse is the case. 



67. The carpus is composed of eight bones. Three lie 

 at the distal end of the ulna ; of them, that on the ulnar 

 side, considerably smaller than the others (and often 

 removed in preparing the skeleton), is the J>isiform; 

 next it is the cu?ietfor?n (os ulnare) which articulates on 

 its proximal side with the ulna ; the third bone of the 

 proximal row is the semilunar {os intermediufu)^ which 

 articulates above with the ulna, and on its radial side 

 with the side of the projecting end of the radius. 



68. The distal end of the radius articulates with the 

 proximal end of the largest bone in the carpus, w^hich 



