428 Wortman — Studies of Eocene Mammalia in the 



The Pes. (Plate VIII.) — As a whole, the pes is very dog- 

 like in general appearance ; the loss of the hallux, the com- 

 pressed, elongated, and highly interlocking character of the 

 metatarsals, as well as the distinctive " sqnare-cut " aspect of 

 their distal ends, recalls at once the hind foot of the dog. 

 There are, however, some important differences which will be 

 pointed out in the course of this description. The astragalus, 

 if found dissociated from the other parts of the skeleton, and 

 if the head were not so convex from 

 60 before backwards, might readily be mis- 



taken for that of a Perissodactyle Ungu- 

 late. Indeed, it furnishes just such a 

 transitional stage as we may readily 

 believe to have jDreceded the peculiarly 

 specialized type of this bone in the Artio- 

 dactyla. The trochlear surface is deeply 

 Figure 60.— Tibia and grooved, the head is set rather obliquely 

 fibula of Dromocyon vorax upon t j ie } 30( j v k y a moderately elongated 



Marsh; end view; three- L i -, ., " ■%• d , i -, • -,• • -i -i • . 



fourths natural size, neck, and its distal end is divided into 

 (Type.) two unequal facets. Of these the larger 



is internal, slightly concave from side to 

 side, and articulates with the navicular ; while the outer is 

 narrow, much prolonged upon the posterior surface, and articu- 

 lates with the cuboid. The calcaneal facet is narrow and 

 deeply concave from above downwards, while the sustentacu- 

 lar facet is broad, slightly convex, and more or less pyriform 

 in outline. There is no astragalar foramen. As compared 

 with the astragalus of the dog, the transverse axis of the head 

 coincides more nearly with the transverse plane of the trochlea ; 

 the calcaneal facet is narrower, and the sustentacular facet is 

 broader. 



The calcaneum has a relatively longer tuber than that of the 

 dog, but otherwise the two agree very closely. The cuboid is 

 proportionally larger than that of the dog. Proximally there 

 is a distinct facet for the astragalus, but otherwise the articu- 

 lar surfaces are much alike in the two. In the posterior aspect, 

 however, they differ considerably ; in the dog the cuboid has a 

 double peroneal tubercle, of which the smaller is external and 

 just above the commencement of the peroneal groove, and the 

 other, larger, is located near the center of the posterior sur- 

 face. The direction of the peroneal groove, which is large, is 

 downwards and inwards. In Dromocyon there is but a single 

 large elongate tubercle, occupying nearly the whole of the 

 posterior surface. Beneath the distal extremity of this tubercle 

 is a notch, which is converted into a distinct groove upon the 

 outer surface of the bone, marking the course of the long 

 peroneal tendon. In the dog the tendon passes obliquely 



