CONDYLARTHEA. 459 



prominent external ridge which descends forwards from the base of the 

 astragalar condyle to the external angle of the cuboid facet, which is want- 

 ing in the Hyrachyus. The posterior extremity is truncate, excepting a 

 tuberosity of the inner edge, which is acuminate. 



The navicular is wider than deep, and has a notch in its posterior bor- 

 der. There is a short tuberosity' on the postero-external corner. The ex- 

 terno-posterior angle is somewhat produced, but it does not extend to the 

 posterior side as in H. agrestis. The cuboid is a robust bone longer than 

 wide. Its proximal face is wider than deep, is straight and oblique down- 

 wards and outwards transversely, and modei'ately convex anteroposteriorly. 

 The tuberosity looks downwards, and extends across the entire posterior 

 face, including a deep transverse groove. The ectocuneiform is much the 

 largest of the cuneiforms ; its is twice as long as the mesocuneiform, and a 

 little wider. Its outline in front would be square but that a concavity exists 

 on the distal half of the external face. The anterior face of the mesocunei- 

 form is a transverse parallelogram. The entocuneiform is a flat bone, as 

 long as the ectocuneiform, and with a narrow anteroposterior articulation 

 with the navicular. Its external face is straight longitudinally and convex 

 anteroposteriorly. It is a little wider anteroposteriorly below than above. 

 Its inner face is half in contact with the mesocuneiform and half with the 

 second metatarsal 



The proportions of the metatarsals are a good deal like those of the 

 metacarpals. The length of the first is two-fifths that of the third, and that 

 of the fifth is one-half that of the third. The second has a lateral facet for 

 the ectocuneiform; the others have a single proximal facet. The second 

 and fourth reach to the distal ligamentous fossse of the third. The middle 

 three are i-ather robust, especially distally. The distal condyles are seg- 

 ments of plane transvei-se cylinders, interrupted postei-iorly by the short 

 obtuse keel. A shallow transverse groove bounds the condyles proximad 

 in front, being better marked than in the anterior foot. The proximal ex- 

 tremity of the first metatarsal is compressed, and the distal extremity is 

 compressed and oblique. The proximal extremity of the fifth has two faces, 

 the internal, naturally, for the fourth. The external is a tuberosity which 

 nearly touches the posterior tuberosity of the cuboid. 



