1 92 SHUFELDT. 



or carpus. The interosseous space existing between the articulated ulna 

 and radius is long and narrow. From a study of the various articula- 

 tions of the antibrachium it would appear that during life the power 

 of pronation and supination must be somewhat limited. 



A very considerable amount of atrojihy marks the development of the 

 ulna of Cynocephalus. To some slight extend this involves the head of 

 the bone, but is far more evident in the shaft. (Plate III, figure 9.) 



On the whole the ulna is very straight from one extremity to the 

 other, straighter distally than represented in figure 9, where some cur- 

 vature is shown due to long maceration and subsequent drying. It has 

 an average length of 12.1 centimeters, or is practically of the same length 

 as its companion in the antibrachium; it holds a postaxial position with 

 respect to the latter in the normally articulated skeleton. Among other 

 mammals, where the ulna is fully developed, it is a much longer bone 

 than the radius, due principally to its extension at the elbow. This is 

 the case in man, in the Felidse, and in many other mammals. 



In the subject here under consideration the shaft of the ulna below 

 the head is considerably compressed from side to side and longitudinally 

 grooved for some little distance on its radial aspect, thus giving rise to 

 a sharp margin for the attachment of the interosseous membrane. Prom 

 its coronoid process to its distal apex the shaft contracts very gi-adually 

 and uniformly, and where the lateral flattening ceases it becomes more 

 or less compressed in the opposite direction, a condition which continues 

 to its distal end. On its outer surface this flatness is continuous from 

 one end of the bone to the other. In human osteology this outer surface 

 is described as the posterior surface of the ulna.^^ 



Distally, the ulna is carried finally to a very sharp apex, or point, 

 which in the articulated skeleton is found just above the styloid process 

 of the radius. This point, together with the lower fourth of the bone, 

 is closely applied to the shaft of the radius and is held there by a firm 

 ligamentous attachment. That it ever actually anlcjdoses with the radius 

 is very much to be doubted, as ordinary maceration is quite sufficient to 

 separate the two completely. 



Proximally, the greater sigmoid cavity is circularly concave and not 

 very wide, although withal of good size ; it is overarched by the olecranon, 

 which is here concave on its summit, uniformly thick from before, back- 

 ward, and pretty well fills the deep olecranon fossa of the humerus when 

 the limb is fully extended. There is not the slightest evidence of any 

 longitudinal division of the greater sigmoid cavity by a raised central 

 ridge as in man and other mammals. 



Both the lesser sigmoid cavity and the coronoid process are well deve- 

 loped, the former being but very slightly concaved with its limiting 

 margin sharp and circular in outline. On the radial aspect of the head 



=' Gray's Anatomy (1870), fig. 158. 



