126 
Annals of the Transvaal Museum 
articulation surface are divided by a groove. The two collateral pits are 
deep. The articulation surface runs right round on the lower border of the 
medial collateral pit. The lateral portion is drawn out to a point above the 
lateral collateral pit and also below it. The lower surface is sharply concave 
immediately behind the groove dividing the portions of the articulation 
surface. 
Metacarpale II is the longest. Its proximal articulation surface is tri- 
angular (text-fig. 27). The whole surface is convex. Laterally it runs out 
into a narrow strip. This is the proximal face of a very high, thin ridge, 
which subsides on the shaft before reaching the distal end. A ridge runs from 
one of the corners of the proximal surface over the upper surface of the bone 
towards the distal end, and disappears before reaching the middle of the shaft. 
The lower surface of the proximal end has a broad, low ridge, which starts 
near the proximal surface and runs towards the middle of the shaft. There 
is a small concavity on both sides of this ridge. The inferior part of the distal 
end is much broader than the superior part, for the medial collateral pit opens 
upwards and inwards. Both collateral pits are deep. A division of the distal 
articulation surface is only indicated. The articulation surface passes much 
further on to the lower than on to the upper surface of the bone. The distal 
end is twisted somewhat to the lateral side. 
Text-fig. 27. Massospondylus Browni. Left hand. Outline in relative position of 
proximal ends of metacarpalia. Metacarpale V is deformed and could not be 
fitted into position. Nat. size. 
Metacarpale III. This is shorter and much more slender than II. Its 
proximal articulation surface is also triangular. The three ridges running from 
the corners of the proximal surface along the sides and upper surface of the 
shaft towards the distal end subside in the shaft before reaching its middle. 
The lateral portion of the lower surface of the proximal end is concave; its 
narrower medial portion is occupied by a broadly rounded ridge, which sub- 
sides in the middle of the shaft. The inferior part of the distal end is broader 
than the upper part, because both collateral pits open upwards. The articu- 
lation surface passes further on to the lower than on to the upper surface of 
the bone. The distal end is twisted somewhat to the lateral side. 
Metacarpale IV is more slender than III. Both its ends are relatively 
thicker. The proximal end has a triangular shape (text-fig. 27), but the upper 
angle does not lie in the middle of the upper surface as in the metacarpalia II 
and III, but on the extreme medial side. The upper angle is a thick rounded 
knob, which continues on to the shaft for a very short distance only. The 
lower medial angle is sharp and it sends a very short, sharp ridge forwards. 
The lateral angle is broadly rounded. The distal end is narrow and thick. 
The upper and lower breadth is practically the same. The shaft has a tri- 
