61 



368. The distal epiphysis of the right femur of a Megalonyx, from Big-bone- 



cave, Tenessee : this differs from the corresponding part of the thigh-bone 

 in the Megatherium, Mylodon and Scelidotherium in having the rotular 

 articular surface separate from the outer and inner condyloid surfaces. 

 The internal condyle is more prominent and convex than the external 

 one, in which respect the femur of the Megalonyx resembles that of the 

 Megatherium more than that of the Mylodon. 



The original is figured and described by Dr. Harlan, Medical and Phy- 

 sical Researches, p. 327, pi- xiv. fig. 19. 



369. The left tibia, wanting the distal epiphysis, of a Megalonyx, from Big- 



bone-cave, Tenessee. The depth of the concave surface for the internal 

 condyle agrees with the character above described in the distal articulation 

 of the femur. The smaller surface for the outer condyle is slightly con- 

 vex, raised above the level of the inner concavity, and confined to the 

 posterior part of the outer half of the head of the tibia, which is rough 

 anteriorly for ligamentous attachment. The original is figured and de- 

 scribed by Dr. Harlan, loc. cii., p. 328, pi. xiv. figs. 20 and 21. 



370. The distal epiphysis of the right tibia of a Megalonyx. The articular 



surface is divided into three facets, but less conspicuously than in the 

 Megatherium or Mylodon. The anterior facet is concave, and was 

 adapted to the anterior convex protuberance of the astragalus which 

 characterizes that bone in the Megatherioid animals : it is narrower ver- 

 tically, but broader and shallower than in the Megatherium or Mylodon : 

 the posterior and largest surface is concave on the inner and convex on 

 the outer half, but slightly so in both : the outer surface slopes upwards 

 from the middle or posterior surface, holding the place of the outer mal- 

 leolus as in other Megatherioids, and was adapted to the upper of the two 

 distal articular surfaces in the fibula. The inner malleolus is slightly 

 produced, and is characterized by the wide and deep oblique groove at its 

 posterior part, separating it from the articular surface. The original speci- 

 men is described and figured by Dr. Harlan, loc. cit., p. 329, pi. xiv. fig. 23. 



371. The right os calcis of the Megalonyx, from Big-bone-cave, Tenessee. It 



