Annals of the Transvaal Museum 125 
on to the proximal end of the first metacarpale in such a way that the upper 
edge of the bone lies at the same level as the upper edge of the proximal 
articulation surface of the first metacarpale. In this case the lower and the 
medial edges of the carpale project downwards beyond the lower edge of the 
articulation surface of the metacarpale. The ridge on the anterior surface of 
the carpale will then lie on the lateral proximal edge of the metacarpale, so 
that the whole concave lateral portion of the anterior surface of the carpale 
projects beyond the lateral side of the metacarpale. 
Second carpale (PI. XVII, fig. 6). The greatest dimension of the bone is 
2*5 cm. When fitted in position, this dimension runs from above downwards 
and inwards. Its breadth is 13 cm. Its thickness below is 1 cm. and above it 
ends in a sharp edge. Its posterior surface is convex and its anterior surface 
concave. Its nearly square lower surface is flat and has a pit in the middle 
for the attachment of a ligament. 
The second metacarpale fits exactly with its convex posterior surface into 
the concave lateral portion of the anterior surface of the first metacarpale. 
Its upper end lies in this case near the lateral production of the lateral border 
of the first metacarpale, and its lower surface lies practically in the same 
plane as the lower proximal edge of the first metacarpale. The two ligament 
pits are then exactly opposite each other. When the second metacarpale is 
now fitted into place, it will be found that its proximal surface lies practically 
at the same level as that of the first metacarpale. The second carpale appears 
to be situated between the second metacarpale and the first carpale, while 
on its medial side it touches the first metacarpale and on its lateral side would 
probably touch the third carpale. 
Hand. 
Both hands are complete, but the left one is much better preserved than 
the right. The hand will be described as if it were stretched out with the 
palmar side downwards. Compare also PI. XVIII, fig. 5, PI. XIX, fig. 1 and 
text-figs. 26 and 27. 
Metacarpale I can easily be recognised from the others by its remarkable 
shape (text-figs. 26 and 27). The proximal articulation surface has a quad- 
rangular shape. The two lateral corners of this 
quadrangle are drawn out and far apart, while 
the two medial corners are rounded and close 
together. The shaft is very short. Two ridges 
run towards the distal end from the lateral 
corners of the proximal end. The ridge starting 
at the lower lateral corner is sharp and high and 
ends in the middle of the shaft. The superior 
lateral ridge is also high and sharp, but it runs 
right down to the distal end, where it branches 
around the lateral collateral pit. The lower 
medial corner of the proximal articulation 
surface is nearer to the distal end than other 
parts of the surface. The axis of the distal 
articulation surface is not parallel with that of 
the proximal surface. Its lateral end is higher 
and its medial end lower than in the proximal 
axis and moreover the lateral end projects much 
further distally than the medial end. The distal 
end is therefore twisted to the medial side. The two portions of the distal 
Text-fig. 26. Massospondylus 
Browni. Metacarpale I of 
the left hand. Outline view 
from above and slightly 
medial, showing the extent 
to which it was covered 
with cartilage. Nat. size. 
9 
