Annals of the Transvaal Museum 
123 
surface stands at right angles to the axis of the bone. The ulnar condyle is 
broad and not thick, the radial condyle is narrow and thick. Thickness of the 
ulnar condyle 2-5 cm., of the radial condyle 3-5 cm. Breadth of the ulnar 
condyle about 3 cm. and of the radial condyle 1-5 cm., all of the left humerus. 
Ulna and Radius. 
Both lower arms are present. Ulna and radius of the right arm have 
suffered badly from pressure. Those of the left arm have also suffered, but 
they are in better condition than those of the right. 
Ulna. The left ulna (PI. XVIII, figs. 2 and 4) has a length of 14 cm. The 
postero-medial edge of the bone has a sig- 
moidal shape, its upper end being convex and 
its lower end concave inwards and forwards; 
the antero-lateral edge is proximally concave 
outwards, in the middle straight or slightly 
convex and its lower end again concave 
towards the lateral side. The proximal end 
is slightly bent forwards and runs out an- 
teriorly into a sharp point. The posterior 
portion of the proximal end is much higher 
than the anterior portion, the difference in 
height being 1-7 cm. This portion is dome- 
shaped ; in front of it lies the concave articula- 
tion surface. The antero-medial border of the 
proximal surface (text-fig. 23) is sigmoidal. ft ulna.^OuUine 
of proximal end seen from 
above. Anterior end below 
and antero-medial border to 
the left. Nat. size. 
Its anterior end is convex; in the middle it is 
concave and its extreme posterior end is 
convex. The lateral border of the proximal 
surface is slightly concave, while the hinder 
border is convex backwards and upwards. The proximal surface has a 
triangular shape. The anterior angle is very sharp; the postero-medial angle, 
formed by the antero-medial border and the hinder 
border, is also acute, but broadly rounded, while the 
latero-posterior angle, formed by the posterior and 
lateral borders, is obtuse. The shaft is concave below 
the lateral border of the proximal surface. Below 
the posterior border the surface of the shaft is concave 
in one bone and convex in the other; it seems that 
the concavity is wholly due to pressure and that, 
therefore, the bone was originally convex in this 
region. In both cases the latero-posterior angle of ^ assos ^ on ' 
the proximal surface and the surface of the shaft for 
a short distance beneath it stand out from the bone 
backwards and outwards. The antero-medial border 
of the proximal surface has a length of 5*4 cm.> the 
lateral border a length of 4 cm. and the hinder border 
a length of 3-2 cm. The thickness of the bone, taken over the latero-posterior 
angle, is 2*4 cm. The antero-medial surface of the bone is concave from the 
antero-lateral border to the postero-medial border. Whether this was originally 
so in the middle of the shaft is not certain. The postero-medial edge of the whole 
bone is broadly rounded ; a large portion of its upper end is rough and served 
for the attachment of muscles. The upper part of the antero-medial surface 
is covered with short longitudinal grooves, which probably served for the 
dylus Browni. Left 
ulna. Outline of distal 
end seen from below. 
Medial end to the left, 
posterior border be- 
low. Nat. size. 
