PElilSSODACTYLA. 
267 
This was evidently a very abundant animal during the Eocene period 
in New Mexico. 
Hyracotherium agile. Marsh. 
OroMppus agilis, Marsh, Amer. Journ. Sci. and Arts, 1873, p. 407. 
Some superior molars agree in size and other characters with those 
noticed by Professor Marsh under the above name, so far as I can ascertain. 
Hyracotherium cuspidatum, Cope. 
Plate Ixv, fig. 18. 
OroMppus cuspidatus, Cope, System. Cat. Eocene New Mexico, U. S. Geog. Survs. W. 
of 100th M., 1875, p. 22. 
This is the least species of the genus known to me, and is known espe¬ 
cially from a portion of the left maxillary bone, which supports the first and 
second true molars. Other separated molars of the same character are not 
uncommon, and probably belong to the same species. 
The molars are characterized by their regularly quadrate form, the 
anterior external angle not being produced as in most of the species. The 
first is also as long as broad, and is not narrowed as in others. Both molars 
are entirely surrounded by a strong cingulum, which is not interrupted on 
the inner side of the crown, and rises into a low accessory cusp at the ante¬ 
rior external angle. The tubercles of the tooth are conical; the outer circular 
in section, and slightly connected by a ridge at the base. The median tu¬ 
bercles are well separated from the interior, and are conical, thus differing 
from other species. The enamel is coarsely rugose. The malar ridge ovei*- 
hangs the maxillary face in a marked manner. 
The specimen described is a portion of an adult animal, and the crowns 
of the teeth are not much worn. 
HYRACHYUS, Leidy. 
Leidy, Report U. S. Geol. Siirv. Terrs., i, p. 59.—Cope, Ann. Report U. S. Geol. Surv. 
Terrs., 1872, p. 594. 
Hyrachyus singularis, Coi^e. 
Plate Ixvi, fig. 17. 
System. Cat. Vert. Eocene New Mexico, U. S. Geog. Survs. W. of 100th M., 1875, p. 19. 
Represented by the maxillary bones and teeth of two individuals, one 
of which includes those of both sides of the cranium, with the molars and 
