74 Annals of the Carnegie Museum. 



head, of the shaft of the radius is straight and moderately compressed, 

 the balance of the bone being greatly curved for its entire length, this 

 curvature having its concavity toward the interosseus space in the artic- 

 lated skeleton. The shaft gradually, though moderately, increases in 

 caliber for its lower four-fifths, presenting three sharp borders, the 

 surfaces between them exhibiting longitudinal grooves. Callithrix 

 also possesses a radius like this, but in it these grooves are absent. 

 Both have a circulai head with a moderate central depression at its 

 summit, and the distal extremity larger than the proximal. The 

 bicipital tuberosity is elongate and not perceptibly raised above the 

 surface of the shaft. Distally the styloid process is fairly well-pro- 

 duced, and this epiphysis does not unite with the shaft until late in life, 

 a remark which also applies to the ulna, and, as already stated above, 

 to the head of the humerus. 



The Ulna. Lasiopyga has an unusually straight ulna, it being slightly 

 curved in the marmosets. It gradually diminishes in caliber from the 

 big olecranon to the distal end, where we find a styloid process present, 

 and articulation with the carpus takes place, which is not the case 

 with this extremity of the radius. Lasiopyga has the greater and 

 lesser sigmoid cavities of the ulna extensive and very concave; in 

 fact, this end of the bone very much resembles the proximal end of the 

 ulna in man. In the Green guenon its shaft is deeply and longi- 

 tudinally grooved for the lesser sigmoid cavity down to a point about 

 its middle. Below this point the shaft is more or less cylindrical in 

 form. 



The Carpus and Manus. Coming now to the carpus and the manus, 

 Mivart has pointed out that the "carpus consists, in Troglodytes, of the 

 same eight bones as in man. In all the other genera there is a ninth 

 bone, the intermedium." Flower in the third edition of the Osteology 

 of the Mammalia, on page 286, figures the bones of the carpus of a 

 Baboon {Cynocephalus anubis) where the intermedium is present, and 

 there called the centrale, so there are also in the wrist-joint of this 

 animal nine bones. In the Baboon there is also another bonelet present, 

 it being the "radial sesamoid," which is free and articulates with the 

 margins of the trapezium and scaphoid. It belongs to the tendon of 

 the flexor carpi radialis muscle. All this agrees with what we find in 

 the carpus of Lasiopyga and Callithrix, in each of which genera the 

 unciform is larger than the magnum, and the pisiform very prominent, 

 and in articulation making a right angle with the shaft of the ulna. 



