Geology and Paleontology. 449 
Hippidium and some from Hippotherium through the intermediate 
form with the molar teeth of the latter genus, and the single 
metapodials of the former. This genus has not been named, and I 
will now call it Hippodactylus, and give as the type Hippotherium 
antelopinum of Falconer from the Sivalik formation of India. 
It enters the Equide. 
We find in this essay two new family names, whose introduction 
we regret. One of these is the “Hyracotheriide,” which is perhaps 
a misapprehension of my own Hyracotheriine. This group cannot 
be separated as a family from the Lophiodontide so far as I can 
see, The other family name is Pachynolophide. Pachynolophus 
was based by Pomel on the P. duvali, which is an undoubted mem- 
ber of the family Lophiodontide, if the figure of Pictet (Traité de 
Palzontologie) is correct, and 1 believe it to be so after examination 
of specimens in Paris. But Lydekker and Pavlow place in this 
genus the Hyracotherium siderotilicwm Pictet, an animal which is 
not only no Pachynolophus, but is not even a member of the 
Lophiodontide. Supposing its digits to be 4-3, it will enter the 
Menodontide, where I have AP it, making it the type of the 
genus Acoéssus. How many of the species referred to Pachynolo- 
phus belong to Acoéssus I do not know, but in any case neither 
genus is a type of a separate family. 
A further acquaintance with the American literature would have 
ved some minor errors. Thus it is stated that the limbs of Pro- 
tohippus have not been described. They were described by me 
in 1873 (Annual Report U. S. Geolog. Survey Terr.), and were 
figured by Wortman in the Revue Scientifique, 1883, p. 712, from 
my blocks, The ancestral relation of Phenacodus to the Dip- 
larthrous ungulate series, is ascribed to Wortman; but this view 
was published by the present writer long before that gentleman. 
The synonym Orotherium is ascribed to Cope instead of to Marsh. 
Merychippus is not different from Protohippus.—£. D. Cope. 
HAYDEN MEMORIAL GerotocicaL Funp.—Mrs. Emma W. 
* Classificati | 
Society, 1881, on of the Perissodactyla. Proceedings Amer. Philosophical 
