Cope.] 392 [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 
Hyrachyus eximius. The trochlea of the astragalus is narrower and more 
deeply grooved. The crests are obtuse, and not so narrowed as in Meso- 
hippus bairdt, 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 UM. batrdi, 
and has rather the proportions of H. ewimius. The cuboid facet is a bevel 
of the external side of the distal extremity, as in H. evimius, and is not on 
a produced ledge, asin M. bairdt. 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 VM. bairdi. The sustentaculum is 
rather more extended transversely than in H. ewimius, 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 fat, 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 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 fourth 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................00 000 029 
a astragalar face OO sete te iis tw VeOMRe SHEERS .019 
Length of inner malleolus.............. Sista ae Rad SBS 007 
ss astragalus on inner side. .....-..e.eeeee sees 2080 
Depth of trochlea os ES owed dacn sha gcc tess 017 
e head ae ES yieiiatee oie its aioe Gh Gin ye is -0145 
Width of trochlea....... eer eset eses tae si wieas xe OLS 
fe Havicular faceticss vies cdcdncwsceemaane ss + 0195 
Length of head from inner crest of trochlea. sesso seeee 005 
a CL CANCUN gic 2 555 cers locos sytaranasd Soave ave ore Geuaa Sedieers,. 058 
