1018 General Notes. [ December, 
and it would scarcely be necessary to create such a group on that 
character alone. But the genus differs further from the Pertsso- 
dactyla and approaches the Frobvoscidia, in the fact that the astrag- 
alus articulates with the navicular only, and by a universally 
convex surface, as in the Carnivora. . 
The astragalus resembles that of the latter order very closely,and 
differs from that of Hyracotherium and the nearest forms among 
the Perissodactyla. Phenacodus has moreover five well developed 
toes on all the feet, and was probably not entirely plantigrade. 
The cast of the brain case shows that the celebral hemispheres 
were quite small and nearly smooth, and that the very large cere- 
bellum and olfactory lobes were entirely uncovered by them. 
The bones of the two carpal rows alternate with each other, and 
there is a large third trochanter of the femur. The cervical 
vertebrae are opisthoccelous. The systematic position of the 
genus may be schematically represented as follows: 
Order PerissopAcTYLA; ungulate; digits of unequal lengths; 
carpal bones alternating; a postglenoid process. Astragalus 
with proximal trochlea, and without distal double ginglymus. | 
Suborder Diplarthra; astragalus distally plane or concave in 
one direction, and uniting with both navicular and cuboid bones; 
a third trochanter of the femur. The known families belong 
here. 
Suborder Condylarthra; astragalus convex in all directions 
ees only uniting with navicular bone; a third trochanter of 
emur. 
Family Phenacodontide. Molar teeth tubercular ; the premolar 
teeth different from the molars ; five digits on all the feet. is 
Genera; Phenacodus Cope, and very probably Catathleus, Mio- 
clenus, and Protogonia® Cope, and perhaps also Anisonchus Cope: 
hese genera include fifteen species, all from the lower Eocene 
beds. The Condylarthra are then the ancestral type of the 
known FPerissodactyla, that is of the horses, tapirs and rhinoce- 
roses, and of the numerous extinct forms.—£. D. Cope. 
NEW GENUS OF PERISSODACTYLA DIPLARTHRA.—Good specimens 
of the Hyracotherium tapirinum Cope, show that the Asay: 
dentition is uninterrupted from the canine inclusive. It thus dil- 
fers from Hyracotherium which has one or two diastemata, © 
fourth inferior premolar is like the third premolar. The if, — 
tum may then be referred to a new genus under the name ir 
temodon.—E. D. Cope. ; 
_ Nores on Creoponra.—A fine series of specimens of ere 
myx demonstrates the following points: (1) Pachyena Mere 
founded on a superior molar of Mesonyx, and must be suppress eo 
(2) Apterodon Fischer, is the same as Mesonyx. (3) Meson) a 
oe fe AMERICAN NATURALIST, October, 1880. iS 
___ * Proceedings Amer. Philosoph, Soc., September, 1881. 
