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 Perzsso- 
dactyla and approaches the Prodboscidia, 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 Ayracotherium 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 
vertebre are opisthoccelous. The systematic position of the 
genus may be schematically represented as follows: 
Order PerissopacryLa; 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 
distally, only uniting with navicular bone; a third trochanter of 
femur. 
Family Pienaidennde Molar teeth tubercular ; the premolar 
teeth different from the molars; five digits on all the feet. 
Genera; Phenacodus Cope, and very probably Catathleus Mio- 
clenus, and Protogonia® Cope, and perhaps also Anzsonchus Cope. 
These genera include fifteen species, all from the lower Eocene 
beds. The Condylarthra are then the ancestral type of the 
known Perissodactyla, that is of the horses, tapirs and rhinoce- 
roses, and of the numerous extinct forms. 2B D. Cope. 
NEw GENUS OF PERISSODACTYLA DIPLARTHRA.—Good specimens 
of the Hyracotherium tapirinum Cope, show that the superior 
dentition is uninterrupted from the canine inclusive. It thus dif- 
fers from Hyracotherium which has one or two diastemata. The 
fourth inferior premolar is like the third premolar. The 4. ¢apir- 
inum may then be referred to a new genus under the name Sys- 
temodon.—E.. D. Cope. 
Nores on Creoponta.—A fine series of specimens of Meso- 
nyx demonstrates the following points: (1) Pachyzna was 
founded on a superior molar of Mesonyx, and must be suppressed. 
(2) Apterodon Fischer, is the same as Mesonyx. (3) Mesonyx 
1 AMERICAN NATURALIST, October, 1880. 
2 Procecdings Amer. Philosoph. Soc., September, 1881. 
