690 THE ERIDGEE FAUNA. 



The posterior foot is both relative!}- and absolutely smaller than that of 

 Hyrachyus eximius. The trochlea of the astragalus is narrower and more 

 deeply grooved. The crests are obtuse, and not so narrowed as in Anchi- 

 therium hairdi, nor are the malleolar facets of the astragalus so sharply defined 

 as in the latter species. The external ligamentous fossa is, however, deep, 

 and is bounded anteriorly by a low trihedral tuberosity not found in the A. 

 bairdi. The head of the astragalus is not sessile as in A. bairdi, and has 

 rather the proportions of E. eximius. The cuboid facet is a bevel of the 

 external side of the distal extremity, as in H. eximius, and is not on a pro- 

 duced ledge, as in A. bairdi. The internal tuberosity of the head is not as 

 much developed as in either of the species named. The navicular face of 

 the asti-agalus is horizontally divided by a shallow ligamentous fossa. The 

 calcanenm is much like that of Hyrachyus eximius. The cuboid face is less 

 oblique than in that species, in the anteroposterior direction, and is less 

 crescentic in outline than in A. bairdi. The sustentaculum is rather more 

 extended transversely than in H. eximius, but resembles that species more 

 than the A. bairdi, in wanting the deep groove at its base on the inferior 

 side, which cuts it off from the rest of the calcaneum. The remainder of 

 the inferior surface is flat, and not grooved for a tendon as in H. eximius. 



The remainder of the tarsus includes the usual five bones, the three 

 cuneiforms being present. They are in general a good deal like the corre- 

 sponding bone of Hyrachyus eximius. The navicular differs in having a low 

 transverse ridge on its proximal face, which fits the groove of the astragalus 

 already mentioned. The hook of the cuboid is large. The external (ante- 

 rior) face of the mesocuneiform has one-third the superficial area of the 

 anterior face of the ectocuneiform. The entocuneiform is rather large, and 

 is flat and subsemicircular. Its position is externo-posterior. The ecto- 

 cuneiform presents facets to both the second and fourth metatarsals, that 

 with the latter the largest. The distal halves of the metatarsals are lost. 

 At their proximal portions they are of subequal width, as in Hyrachyus ex- 

 imius, but the lateral ones are rather narrower at the middles of the shafts. 



Measurements. 



M. 



Width of distal extremity of tibia 029 



Width of astrasralar face of tibia 019 



