THE HIND LIMB AND FOOT. 



63 



to the front of the tibia." This is probably correct, though I am unable to ascertain that this 

 description was based upon an actual specimen of the bone in question. In Monoclonius, an 

 earlier and smaller form, the fibula was present but rather slender, as shown in fig. 88. 



Fig. 71. — A, Anterior view of left femur of Triceratops prorsus Marsh, No. 4842, U. S. National Museum, in mounted skeleton: Ji, Head; 

 t, greater trochanter; c, internal condyle. B, Front view of left tibia of same. No. 4842, U.S. National Museum, in mounted skeleton: 

 c, Cnemial crest;/, surface for fibula; o. astragalus. C, Distal end of same: a, Astragalus. All one-eighth natural size. After Marsh. 



THE TARSUS. 



The astragalus is the only element of the tarsus known to the present writer, though others 

 were doubtless present. It was closely applied and early became coossified with the tibia, 

 covering over the internal two-thirds of the distal extremity of that bone, as shown in fig. 71 

 and PI. XVI. I am unable to say anything further regarding the structure of the tarsus in the 

 Ceratopsia, no elements other than the astragalus referable to it being known to me. 



THE METATARSUS. 



Three functional metatarsals were present in the pes of Triceratops. These were the second, 

 third, and fourth. It is possible also that vestiges of the first and fifth were present, but as 

 yet no pes has been discovered sufficiently complete to determine this point. The metatarsals 



