1884.] 545 (Cope. 
Measurements. M. 
Length of molar series. see eee a aN OSL 
of § “PYEMOIATA ON DASES Lee a cesee ier vactenvens O41 
Width of canine posteriorly......... ET OGRE .010 
Diameters P-m, iv MaNteroposteuiol. own i ens (OVA OTO 
HYEMSVEISOs Cove VON es ewes ena ew Lae 
Of ,this species I have but two specimens, which were obtained from the 
Ticholeptus beds of Deep river, Montana, by my assistant, J. C. Isaac. 
Merychyus elegans Leidy. 
Proceedings Academy Philada., 1858, p. 24. Extinct Mammalia 
Dakota and Nebraska, 1869, p. 118, Pl. XI, figs. 1-11. 
Niobrara river, Nebraska. 
Merychyus zygomaticus Cope. 
Ticholeptus eygomaticus Cope, American Naturalist, Feb. 1878. Bulle- 
tin U. 8. Geolog. Survey Territories, 1878, p. 880. 
This species is peculiar in having the posterior expansion of its zy go- 
matic arch horizontal instead of vertical. It has a thickened external edge 
which continues into a strong posterior angle which projects behind the 
posterior margin of the postglenoid process. The auricular meatus is 
directed posteriorly in a way quite peculiar, resembling somewhat the 
position seen in some of the hogs. The malar bone is very prominent. 
The infraorbital foramen is above the contact of the third and fourth 
superior premolars. The larmier is large and its maxillary border descends 
posteriorly. a 
In size this species is between the JL elegans and the MW. medius. If 
my identification of New Mexican specimens is correct, this species differs 
from the 4. medius in the much less production of the premaxillary re- 
gion, besides the smaller size. 
Ticholeptus beds of Deep river, Montana ; J. ©. Isaac. 
Merychyus medius Leidy. 
Proceedings Academy Philad’a, 1858, p. 25. Extinct Mammalia, 
Dakota and Nebraska, 1869, p. 119, Pl. XI, figs. 12-14. Cope U. 8. Expl. 
Surv. W. of 100th Mer., G. M. Wheeler, iv, pt. ii, p. 824. 
Niobrara river, Nebraska, Hayden ; Santa Fé, New Mexico, Cope. 
Merychyus major Leidy. 
Proceedings Academy Philada., 1858, p. 26. Extinct Mammalia, Da- 
kota and Nebraska, 1869, p. 121, Pl. X, figs. 15-16. 
This species, known hitherto from Leidy’s descriptions of four of the 
superior molars, is the largest of the genus, and perhaps of the family. 
More information regarding it is much to be desired. 
Headwaters of the Niobrara river ; from Loup Fork beds, according to 
Hayden. 
