
A Skeleton of Great Fossil Beaver, Castoroides Ohioensts. 165 
Castor and Castoroides more marked than in the feet. Whoever 
will look at a beaver’s hind foot will see its fossil ally. 
The astragalus has the usual pulley-like groove, obliquely, from 
before backward, with the shorter and more abrupt slope upward, 
toward the internal malleolus, and its longer and more gradual 
slope upward and outward. ‘The groove is relatively a little deeper 
than in Casfor. Diameter across the upper articular surface, 1.14 
inches ; from process to process, at base, 1.55 inches; greatest 
antero-posterior diameter, 1.51 inches. 
The anterior articulating surface of the head, as it extends 
beneath and backward, is continuous with the surface, which artic- 
ulates with the upper side of the internal process of the calcaneum. 
The calcaneum measures, from tuberosity to antero-interior 
process, 3.25 inches; length of the backward projection, 1.60 
inches ; lateral diameter of tuberosity, 1.15 inches; vertical diam- 
eter of tuberosity, .86. 
The inner projection for the support of the astragalus is rela- 
tively greater than in Cas¢orv, and the tuberosity is more thickened 
vertically. 

Fic. 25 —One-third natural size. Parts belonging to right hind foot: 1, 2. 3, 4,5 
metatarsals in their order from within outward: 5 sits on tubercle underneath the 
base of 4. 
To see the metatarsals in Castor is to see them in Castoroides, 
with but a very slight modification to increase the scale, and a 
little variation as to proportionate length. The fourth metatarsal 
in Castor is the longest and stoutest, yet its pre-eminence in this 
