Cope.l ^^^ [April 15, 



lengths. The median ridge is rather wide ; the inner malleolus is narrow , 

 has no distal facets and no distinct tendinous grooves externally. 



The posterior foot is both relatively and absolutely smaller than that of 

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

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

 Mppus bairdi, nor are the malleolar facets of the astragalus so sharply de- 

 fined 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 M. bairdi. The head of the astragalus is not sessile as in M. bairdi, 

 and has rather the proportions of H. eximius. The cuboid facet is a bevel 

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

 a produced ledge, as in M. bairdi. The internal tuberosity of the head is 

 not as much developed as in either of the species named. The navicular 

 face of the astragalus is horizontally divided by a shallow ligamentous 

 fossa. The calcaneum 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 M. bairdi. The sustentaculum is 

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

 species more than the M. 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 hone 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 ex- 

 ternal (anterior) 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 ectocuneiform presents facets to both the second and fourtli metatar- 

 sals, 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 eximius, but the lateral ones are rather narrower at the middles 

 of the shafts. 



Measurements. M. 

 Width of distal extremity of tibia 029 



" astragalar face " 019 



Length of inner malleolus 007 



" astragalus on inner side 030 



Depth of trochlea " " 017 



" head " " 0145 



Width of trochlea 015 



" navicular facet 019* 



Length of head from inner crest of trochlea 005 



" calcaneum 058 



