112 
Annals of the Transvaal Museum 
and downwards. The lateral part of the distal articulation surface consists of 
an anterior and a posterior portion (text-fig. 17). The anterior portion, which 
is the distal surface of the processus tibiae anterior distalis, occupies a much 
higher position than the posterior portion, which is the distal surface of the 
processus tibiae posterior distalis. The distal surface of the processus posterior 
is continuous with the medial portion of the articulation surface. It slopes 
upwards from the lateral to the medial side and from the posterior towards 
the anterior border. The medial portion of the articulation surface is con- 
nected with the distal surface of the processus anterior by means of a short 
and very steep surface. The distal face of the processus anterior slopes from 
its medial end upwards and outwards, and from its anterior border backwards 
and slightly upwards. Medially the processus posterior is nearly as broad as 
the processus anterior. Towards the lateral side it becomes narrower and it 
terminates in a point. This end is bent very slightly forwards. Both ends of 
the distal surface of the processus anterior are broad, but the inner end is 
slightly broader. Apparently, the lateral end of the processus anterior does 
not project further outwards than the processus posterior. The highest point 
of the lower surface of the processus anterior 
is situated 37 mm. above the lowest part of 
the processus posterior. There is a slightly 
concave surface (sulcus malleoli tibiae) imme- 
diately behind the lateral end of the processus 
anterior. This surface passes downwards be- 
tween the processi and is continuous with the 
concave upper anterior surface of the processus 
posterior ; it passes inwards for a short distance 
only. The breadth of the distal end, along 
the front border of the articulation surface, is 
82 mm. This front border is laterally slightly 
concave and medially, where a small piece of 
the edge is broken off, it is slightly convex. 
The medial border makes an acute angle with 
the anterior border and an obtuse angle with the posterior border. The 
borders round off into each other. The breadth of the medial side, measured 
parallel to the medial border, is 56 mm. The posterior border converges 
slightly with the anterior border towards the lateral side; its length is 60 mm. 
The distance from the anterior medial corner of the distal end to the lateral 
end of the processus posterior is 1 mm. longer than to that of the processus 
anterior. 
A broad high ridge runs down from the tuberositas tibiae in the direction 
of the anterior medial corner of the distal end. It does not reach this corner, 
however, for it terminates at about 6 cm. above the distal end. The surface 
between the lower end of this ridge and the distal end of the bone is concave. 
The lateral anterior edge of the distal end is broadly rounded below. Higher 
up the edge becomes a fairly sharp ridge ; then again the ridge becomes broad 
and low and finally disappears above the middle of the bone. There is a broad, 
oval and very low boss on the lateral side of the bone, below the notch in the 
lateral border of the proximal surface; its upper end lies about 4 cm. below 
the notch and its lower end about 8 cm. Its breadth is about 2-5 cm. The 
thickness of the bone in the middle is 5-5 cm. and its breadth at this place 
about 4 cm. The thickness of the distal end is about 5 cm. 
Text-fig. 17. Dromicosaurus gra- 
cilis. Right tibia. Outline of 
distal surface seen from the 
distal end. Anterior border 
below. Lateral side to the 
right, x T 
