94 THE MKRYCO.IDODONTID/E 



The neck is elongate and constricted, and the great trochanter rises about as high as the proximal end 

 of the articular surface. There is no third trochanter. In fact, these features resemble those of the 

 carnivore more than those of the ungulate type of femur. The digital fossa is deep, which pre- 

 supposes a relatively large obturator extern us muscle. The lesser trochanter, situated slightly on the 

 preaxial side, is conical and relatively rugose. The intertrochanteric lines are rather indistinct, as are 

 the linea quadratl. The shaft (Fig. 62) is almost straight and nearly circular in cross section. The 

 tinea aspera are faintly indicated. The distal end has a considerable anteroposterior diameter. The 

 outer tuberosity is much more prominent than the inner. The internal condyle is the larger and is 

 more rounded than the external. Its articular facet is transversely convex. The articular surface 

 of the external condyle is inclined toward the median line, and the intercondyloid notch is deep. 

 Anteriorly the condyles are continuous with each other, forming a concave depression or trochlea for 

 the patella, which is shield-shaped, flattened on top and on its posterior side, and convex anteriorly. 

 The fibula (Fig. 63) is missing, except for its distal end. The shaft is restored and extended 

 the entire length of the tibia, from which it is separated by a narrow interosseous space. The 

 external malleolus is larger and wider than the internal and articulates with the astragalus by a tri- 

 angular facet. It is externally deeply grooved for the tendons of the peroneus longus and brevis 

 muscles. Its edge is very rugose, affording attachment to the external lateral ligament of the ankle 

 joint. 



Fig. 61. — Eporeodon socidis Marsh. Os innominatum. CT. Cat. No. 13119 Y.P.M. 1/2 nat. size. (After 



Thorpe, 1931.) 



The tibia is similar to that of the artiodactyle type, although somewhat suggestive of that of 

 Canis. The spine is prominent and bifid, affording attachment to the semilunar fibrocartilages and, 

 by clearly marked depressions in front and behind its base, to the crucial ligaments of the joint. 

 The shaft has three sharp ridges. The internal malleolus projects downward below the external, 

 and it is of peculiar shape, being long, stout, and somewhat hook-shaped. This hook is received in 

 a deep depression in the astragalus. It has well-marked grooves for the tendons of the tibialis 

 posticus and flexor longus digitorum muscles and also affords attachment to the internal lateral 

 ligaments. 



The tarsus of Eporeodon resembles that of the pig (Fig. 64), although the astragalus is heavier 

 and wider. The trochlear surface comprises two unequal articular facets, divided by a deep, 

 strongly convex groove. The external condyle is much the longer, terminated anteriorly by a deep 

 fossa, separating it from the cuboidal facet below. The inner condyle is small, with a sharp crest, 

 due to the lateral articulation for the internal malleolus. The distal extremity of the astragalus is 

 divided into two articular facets, the one for the navicular being deeply concave transversely and 

 the other for the cuboid being convex longitudinally and straight transversely, with a slight pitch 

 toward the calcaneum. In Alerycoidodon and Eporeodon the facet for the cuboid is extended around 

 on to the posterior surface. The groove for the tendon of the plantaris muscle is well shown on 

 the inner side of the tuber calcis. The osseous ridge for the attachment of the external lateral liga- 

 ment is very prominent and is situated a little below and to the side of the articulation for the 

 external malleolus. 



The cuboid is not depressed, as it is in Agriochcerus. Its superior surface bears the two facets 

 for articulation with the calcaneum and astragalus, the former being flat and inclined forward and 



