1881.] on the Feet of Mammalia, 543 
III. The trochlear ridges and keels at the various movable 
articulations of the limbs. These are as follows: 
1. Looking downwards— 
‘a, Intertrochlear crests of the humerus. 
f. On the carpal end of the radius, 
_ y. Metacarpals, distal ends. 
6, Tibia distally. 
e. Metatarsals distally. 
2. Looking upwards— 
a, Radius distally. 
@. Astragalus, edges. 
y. Astragalus distally (Artiodactyla). 
6. Phalanges (very weak). 
The following observations may be made respecting the struc- 
tures included under division III: The trochlear keels which . 
look downwards are much the most prominent and important. 
Those enumerated as looking upwards are weak and insignificant, 
or of a different character from the down-looking ones. The 
latter are all projections from the middles of the ends of the 
respective elements. The up-looking are generally projections of 
the edges of bones. Such are the lateral crests of the astragalus, 
Fic. 1 Fic. 2. 
Fic. 1.—Right posterior foot of a species of Coryphodon from New Mexico, one- 
half nat. iis From Report Expl. W. of tooth Mer., G. M, Wheeler, Iv, Pl. urx. 
Fic. 2.-Right posterior foot of Aphelops megalodus Cope, from Colorado, one- 
halt natural size. From Report U. S. Geol. Surv. Terrs., F. V. Hayden, tv, Pl. cxxx. 
and the adjacent edges of the cuboid and navicular bones which 
