PALiEOSYOPS LEIDY, AND ITS ALLIES. 
305 
axis is rotated more to coincide with the vei’tical than in P. pahidosus, thus produc- 
ing a wide unciform-magnum surface for articulation. 
The extensive transverse breadth of the unciform prolongs its articulation 
with the magnum nearly to the median axis of metacarpal III. 
The superior facet of the unciform is obliquely placed and concave from side 
to side ; it is I’ather shallow from behind forward and limited by the posterior tuber- 
osity of the bone. This tuberosity is placed externally and curves outward instead 
of downward as in the Rhinoceros. The unciform-lunar facet is large, very 
oblique, and forms a wide angle with the superior facet for the cuneiform. The 
unciform-magnum facet is small, only allowing about one-third of the interual sur- 
face of the bone to articulate with the magnum. This contact in P. paludosus is 
much larger than in Li7}tnohyops. Comparing this facet with that of the Tapir and 
the Rhinoceros we remark their great difference. In the latter form the unciform 
has a large and more nearly vertical facet for the magnum which is very 
extensive and extends all across the articular face of the bone. The facet 
for metacarpal 111 is large, more so in proportion than in the Tapir, and nearer hori- 
zontal. The inferior surface of the unciform is deeply concave from before back- 
ward, and is subdivided slightly for the two lateral digits of the mauus. Owing to 
the large transverse extent of the unciform, the facet for metacarpal V is large, and 
this digit is not placed so fin- to the side and behind as in the Tapir, in which the 
fifth metacarpal is smaller than in P. paludosus. 
The inferior face of the unciform is not prolonged heyond the magnum like 
that of Tapirtis Imt is nearly on the same horizontal line with it. In fact a hori- 
zontal line drawn beneath the magnum would limit the carpus distally. 
Pelvis, No. 10,232. — The pelvis in P. paludosus is short and broad and its 
general proportions approach very nearly those of Rhinoceros. It agrees with the 
latter form in having the iliac portion longer than the ischial, although in this 
species the ischia are longer proportionately to the ilia than in the Rhinoceros. 
The total length of the os innominata compared with the expansion of the ilia is 
greater in this sjjecies than in the Rhinoceros. 
Diplacodon differs from Palceosyops in having a pelvis much longer and nar- 
rower in comj^arison to its breadth. The external border in Diplacodon is shorter 
and the plane of the gluteal surface is thrown more outward than in Palceosyops. 
Ilium. — The ilia are flat and thin with their external angles inverted. The 
supra-iliac border is not interrupted by a depression as in the pelvis of the Tapir 
but forms a strongly convex border pointing forward and outward. The ischial 
border tapers gradually below and then becomes strongly convex superiorly, where 
it joins the supra-iliac border to form the sacral jjortion, the latter being much like 
that of Rhhwceros in form. The external or acetabular border is rather long and 
deeply concave ; it forms with the supra-iliac border a sharp angle. The pedun- 
cular portion of this border is rounded and terminates at the rim of the acetabulum 
in a prominent triangular tuberosity for the rectus muscle. 
