82 THE SKELETON OF THE CAT. 
fibula. The ventral surface of the distal end presents an ob- 
lique border which passes from the apex of the malleolus 
proximolaterad. The dorsal surface extends into a V-shaped 
projection (g) between the malleolus and the fibular facet. 
The distal end presents an oblique ridge running from the 
apex of the V-shaped extension of the dorsal surface to near 
the base of the medial malleolus. The ridge and the con- 
cavities on either side of it, the medial one of which is deeper, 
fit against the proximal trochlear surface of the astragalus. 
Fibula (//, Fig. 57).—The fibula lies at the lateral side 
of the tibia in the shank. It is a slender triangular-bone with 
enlarged proximal and distal ends. 
The proximal end or head (4)is flattened. It bears a facet 
on its proximomedial surface for articulation with the tibia, 
and is longitudinally grooved on the outer surface. 
The shaft has a very sharp medial border. This border is 
turned toward the tibia and gives attachment to the interosseous 
membrane, which runs between the tibia and fibula. 
The distal end is expanded to form the lateral malleolus (2). 
This bears a facet on the proximal portion of its medial surface 
near its dorsal margin, for the tibia, and distad of this is a 
second facet for the astragalus. The ventral and lateral sur- 
faces are grooved for tendons. 
Tarsus (Fig. 58).—The tarsus consists of seven bones. 
The longest of these, lying on the lateral side of the foot and 
forming the support of the heel, is the calcaneus or os calcis (a). 
It articulates distad with a bone, the cuboid (c), which bears 
the fourth and fifth metatarsals. Lying between the calcaneus 
and the tibia is the astragalus or talus (4), the distal end of 
which. articulates with the boat-shaped navicular or scaphoid 
(d). The scaphoid bears on its distal surface the three cunei- 
form bones, lateral (¢), medial (g), and intermediate, bearing 
the rudiment of the first metatarsal and the second and third 
metatarsals. 
Astragalus. (Talus BNA) (Fig. 58, 6).—The astragalus 
may be divided into body, neck, and head. The body is 
marked on its proximal surface by a deep pulley-like groove 
for the articulation with the distal end of the tibia, and on its 
