64 



THE CERATOPSIA. 



are much longer and stronger than the metacarpals. They interlock with one another at their 

 proximal ends and are closely applied throughout most of their length in order to give greater 

 rigidity and strength to the foot. The median or third is the largest of the three, but the second 

 and fourth are also quite well developed; their shafts are somewhat constricted, but they expand 

 at the extremities. At the distal end the lateral expansion is greatest, while at the proximal 

 end they are expanded most antero-posteriorly. Their form is well shown in fig. 73. 



Fig. 72.— Fibula of Tri- 

 ceratops serratus, No. 

 970, American Muse- 

 um of Natural His- 

 tory, anterior view. 

 One - eighth natural 

 size. Drawn by R. S. 

 Lull. 



Fig. 73. — a, b, c, External, posterior, and internal views of metatarsal of Triceratops prorsus, 

 TJ. S. National Museum, d, e,f. Dorsal, lateral, and palmar views of ungual phalanx of the 

 pes of Triceratops horridus, U. S. National Museum. All one-eighth natural size. After 

 Marsh. 



THE PHALANGES. 



The phalanges of the pes are very similar to those of digits II, III, and IV in the manus, 

 though somewhat larger. The proximal phalanges are rather long, but the intermediate ones 

 are very short and broad. The terminal phalanges are broad and rugose or cancellous. They 

 were incased in flat hoofs instead of compressed claws as in the sauropod and theropod dinosaurs. 

 It is probable that the third digit was provided with four or five phalanges, while the second 

 and fourth digits would each have had one less than the third. 



