2 
18; L. 7; 8.5; C.?; Of the cervicals the seventh only is not pierced by 
the arterial canal. The atlas has a broad flat “transverse ’’ process. 
The digits are 43; the third with a symmetrical hoof, those of the 
exterior digits halved ; the former have two reverted proximal processes, 
the latter, one. The astragalus exhibits a deeply-grooved and extensive 
trochlear are, with rather long neck, which has a greater facet for the 
astragalus, a lesser for the cuboid bone. 
From the above it is evident that this genus is nearly allied to Tapirus 
and cannot be removed to another family. Professor Leidy states that 
the premolars differ from those of Tapirus in having ‘‘but one inner lobe 
connected with the external crest by two transverse crests.’”? The 
appearance of one lobe is produced by the posterior curvature of the 
anterior transverse crest round the inner extremity of the posterior 
crest. 
I now proceed to describe the skeleton more exactly. 
HYRACHYUS EXIMIUS. Leidy. 
Hayden’s Geol. Survey, Montana, 1871, p. 361. 
Cranium. In the specimen to be described, the anterior portion from 
the glenoid cavities is wanting. The sagittal crest is quite elevated, and 
the lateral occipital quite prominent, and continuous below with the 
superior margin of the squamosal portion of the zygoma. Four nutri- 
tious foramina pierce the parietal bone near its middle and above the 
paramastoid process, and two enter the squamosal above the postglenoid 
process. The paramastoid process approaches near the occipital condyle 
by its posterior border. I cannot discover the sutural boundaries of the 
mastoid bone, but that separating the paramastoid process from the 
process in front of it is distinct. The condyle of the mandible is massive 
and the posterior border of the latter extends backwards with a slight 
obliquity. 
Measurements. — M. 
Elevation of sagittal crest above foramen magnum..... 0.045 
Width of bifurcation of crest behind.................. 0388 
ai occiput behind meatus auditorius............ .070 
Width between, inclusive of occipital condyles........ .046 
«temporal fossa at meatus.............0. cee eee .050 
«meatus auditorius............. 0.00. cece eee .012 
« eondyle of mandible.....................0000e .032 
Depth of ramus behind.................0..0 cece eee 095 
In further illustration of the species I add measurements of teeth, etc. 
from another specimen : 
Length of last two superior molars...............20005 041 
ee ast MOlarsccces sys .ees steed oped teed eee .019 
Width Of Jast 25" secs 3 sahedeebaacaraaaaen tse .++ 2022 
Length of inferior molar series...............200.000- -095 
ee OS WPEMOlALS oye ces eistiqeh ses ooiaag a aeaowe Acs costae -040 
ec 
ast anOlary. says weaeseh nea de-abiond eee i hales +021 
