Annals of the Transvaal Museum 
135 
the pulley-shaped articulation surface of the preceding phalanx. The middle 
of both its anterior and its posterior border projects upwards, however an- 
teriorly more strongly than posteriorly. This anterior upper process is strong- 
est in II, 2. The first claw is more bent than the others. All the claw- 
phalanges are unsymmetrical. The medial portion of the articulation surface 
of clawphalanges I, II and III is smaller than the lateral portion. In claw- 
phalanx IV I could see no difference in size. Clawphalanges I, II and III 
hang over towards the lateral side. Clawphalanx IV hangs slightly over 
towards the medial side. In clawphalanges I and II the edge between the 
lateral surface and the lower surface is rounded, while the edge between the 
medial surface and the lower surface is a sharp ridge. In clawphalanx III 
both edges are sharp, although the medial edge is sharper. In clawphalanx IV 
the edges are narrow rounded ridges, the one exactly like the other. In claw- 
phalanges I — III the groove for the claw lies deeper on the medial than on the 
lateral side. In clawphalanx IV the medial groove may be very slightly higher 
than the lateral one. 
The phalanx of the fifth toe has a remarkable shape. It is a flat bone, 
the shape of which is generally triangular. What is probably the proximal 
end has a breadth of i-6 cm. and a thickness of 0-9 cm. What is probably its 
medial side has a length of i*8 cm. and is concave. If this is the right position 
of the bone, which I do not doubt, for the endphalanx of the fifth finger has 
this position and has the same general shape as the present bone, the anterior 
and lateral sides form an evenly convex border. The antero-lateral surface 
is smooth and gives the impression of having been covered with cartilage. 
Its posterior border goes slightly further down than its anterior border. The 
anterior and posterior surfaces of the bone are concave. 
Discussion. 
While comparing the bones of the lower arm with those of the Plateo- 
sauvidae as described by v. Huene ( 5 ), it was found that there were certain 
differences which required an explanation. There is one point which can be 
decided without difficulty and that is, which of the three angles of the tri- 
angular head of the ulna is the anterior one. The articulation surface is of 
course anterior to the high olecranon-like process and the angle below it must 
be the anterior angle. This angle lies between the two long sides of the triangle. 
If the ulna of both arms of our specimen is placed with the anterior angle 
forwards, it will be found that the longest side of the triangular head lies on 
the medial side. According to description with text-figure of ulna and radius 
of Plateosauvus Reinigeri v. Huene it seems to be different at least in this 
species. Here the longest side of the triangular head lies on the lateral (antero- 
lateral) side of the bone, and the angle between the two long sides of the 
triangle lies on the lateral side. The figured right ulna of Plateosauvus Reinigeri 
would have to turn 90° on its axis to place the narrow angle of its upper end 
in front of the remainder of the head. If the narrow angle of the ulnar head 
of Plateosauvus Reinigeri were pointing forwards, its contour would be placed 
in the same position as the contour of the head of our right ulna and one 
would therefore conclude that the described ulna of Plateosauvus Reinigeri 
is also a right one, which it actually is. 
Let us now compare the ulna of our form with the description and text- 
figures of the ulna of Plateosauvus Quenstedti v. Huene. In the text (/. c. p. 36) 
it is stated that the anterior angle lies between a lateral side (the longest) 
of 9 cm. length and a medial side of 7 cm. length. The posterior side has a 
length of 6 cm. An upper view is given of the left ulna in the text-figure. Its 
