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 (//) 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 (/'). 

 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 (V), which bears 

 the fourth and fifth metatarsals. Lying between the calcaneus 

 and the tibia is the astragalus or talus (b), 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 (^), and intermediate, bearing 

 the rudiment of the first metatarsal and the second and third 

 metatarsals. 



Astragalus. (Talus BNA] (Fig. 58, b}. 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 



