1915.]| M atthew and Granger, Lower Eocene Wasatch and Wind River Faunas. O00 
in 1874 (M. chamense) and was based on a single jaw fragment, with upper 
molars, found by him during his explorations of the New Mexican Wasatch 
of that year. A few years later David Baldwin, then collecting for Marsh, 
obtained from the type locality and horizon the remains of many individuals 
of this form. Still later Cope secured from Baldwin a large amount of 
Meniscothertum which, judging from its appearance, came from the same 
“pocket” or bone bed as the Yale material. Both of these collections con- 
sisted of badly disorganized skeletons and more or less fragmentary skulls 
and jaws, all in a hard brick-red matrix. Cope selected from his material 
two jaw specimens, the largest and the smallest, as types of two additional 
species (MV. terrerubra and M. tapiacitis) and figured most of the elements 
of the skeleton except the feet. Marsh from his collection figured a fore 
and a hind foot under the new name Hyracops socialis and created the 
ordinal name Mesodactyla to include the two genera of Meniscotheridee 
He differentiated Hyracops from Meniscothericum by the last molar being 
nearly or quite like the molars, by there being four vertebree in the sacrum 
instead of three, and by doubtful and unspecified differences in the feet. 
An examination of all of the specimens of this group in the Yale Museum ! 
shows no specimens marked as types of Hyracops and none which shows 
generic differences from the Meniscotherrum 
types and referred material in the American 
Museum collection. Two fairly complete fore 
feet, both with the carpals disarranged and 
partly obscured by matrix, apparently formed 
the basis for the figures of the fore foot of 
Hyracops, while a few isolated but well pre- 
served bones of the hind foot seem to have 
served for the reconstruction of the pes. Com- 
pared with the feet of the composite skeleton, . Fig. 15.  Meniscotherium 
‘ ; | a ~y terrerubre, carpus and meta- 
assembled from the materials of the Cope Col- carpus, seen from the front. 
lection,? the pes is very similar. In the fore From the composite mounted 
‘ p “~ . skeleton, No. 4412, in the 
foot one very important difference is observed; Amer. Museum. 
in Marsh’s figures of Hyracops the magnum 1s 
unusually large, the front surface being nearly twice that of the oe and 
it is in articulation with the cuneiform. In the American Museum speci- 
men the magnum is smaller than the lunar and 1s separated from the 
cuneiform by the unciform which articulates with the lunar. The cen- 
trale is not preserved but its existence in this form 1s indicated by the 
WV oh it eZs 
The writer wishes to express his appreciation of the courtesies extended, in this con- 
nection, by Prof. Charles Shuchert of the Yale Museum. 
2 See Osborn, 1910, Age of Mammals, p. 125, fig. 39. 
