PLATE XXIII. 



Astragalus in different genera of Megatherioids, one-third the natural siz 



Fig. 1. Upper surface of the astragalus of the Mylodon robustus. 



Fig. 2. Under surface of the astragalus of the Mylodon robustus. 



Fig. 3. Upper surface of the astragalus of a Megalonyx ? j- - y'^/<rt/-e^\ 



Fig. 4. Under surface of the astragalus of a Megalonyx ? 1 It^'/C /^w-t^n^u- '< ■ 



Fig. 5. Upper surface of the astragalus of the Megatherium. 



Fig. 6. Under surface of the astragalus of the Megatherium. 



Fig. 7. Upper surface of the astragalus of the Scelidotherium leptocepholvm. 



Fig. 8. Under surface of the astragalus of the Scelidotherium leptocephalum. 



a. External trochlear convex ridge of the tibial articular surface. 



b. Internal tuberosity of the tibial articular surface. 



c. Upper portion of the navicular articulation. 



d. Cuboidal articulation. 



e. Anterior part of calcaneal articulation. 

 /. Posterior part of calcaneal articulation. 



I 



