The Skeleton 83 
cavity, and a larger, somewhat bilobed surface for 
articulation with the radius and ulna. On its 
ventral side, near the proximal end, is a very 
prominent protuberance, the deltoid ridge. The 
ulna (u) is slightly heavier and longer than the 
radius and forms the greater part of the elbow joint 
and about half of the wrist joint. Its proximal 
‘end is considerably larger than the distal, but has 
no olecranon process. Its distal end articulates 
with the ulnare and pisiform. The ulna as a whole 
is slightly curved, while the radius is quite straight. 
The radius (r) consists of a cylindrical shaft with 
enlargements of about equal size at the ends. 
The proximal end articulates with the side of the 
ulna and with the humerus; the distal end with 
the radiale. 
The carpus consists of a proximal row of three 
distinct bones and a distal row of smaller and less 
fully ossified elements. Of the proximal row the 
vadiale (r’) is much the largest bone. It is hour- 
glass shaped, with the proximal end somewhat 
larger than the distal. Proximally it articulates 
mainly with the radius but also slightly with the 
ulna and ulnare. Distally it articulates with the 
centrale. The ulnare (u’), the second bone in size 
in the wrist, has about the same shape as the radiale 
but is much smaller. Proximally it articulates 
with the pisiform, radiale, and, apparently, with 
the ulna; distally it is in contact with the fused 
carpalia elements. The pisiform (p) is a small, 
