or horned Dinosaurs, of North America. 175 



The Posterior Limbs. 



The femur is short, with the great trochanter well developed. 

 The shaft is comparatively slender, and the distal end much 

 expanded. The third trochanter is wanting, or represented 

 only by a rugosity (Plate YIII, figure 1). 



the tibia is of moderate length, and resembles that of 

 Stegosaurus. The shaft is slender, but the ends are much 

 expanded. The fibula is. very slender, and the distal end was 

 closely applied to the front of the tibia (Plate YIII, figures 

 2-3). In adult individuals, the astragalus is firmly eoossified 

 with the distal end of the tibia, as in Stegosaurus. 



The metatarsal bones which were functional are rather long, 

 but massive. Their phalanges are stout, and the distal ones, 

 broad and rugose, indicating that the digits were terminated 

 by very strong hoofs (Plate IX, figures 7-12). 



All the limb bones and vertebrae in Triceratops, and the 

 nearly allied genera, are solid. 



The Dermal Armor. 



Beside the armature of the skull, the body also in the 

 CeratqpsidcB was protected. The nature and position of the 

 defensive parts in the different forms cannot yet be determined 

 with certainty, but various spines, bosses, and plates have 

 been found, that clearly pertain to the dermal covering of 

 Triceratops, or nearly allied genera. Several of these ossifica- 

 tions were probably placed on the back, behind the crest of 

 the skull (Plate X), and some of the smaller ones may have 

 defended the throat, as in Stegosaurus. 



The remarkable extinct reptiles here briefly described pre- 

 sent many characters which separate them widely from all 

 other known Dinosaurs. Some of these characters are evi- 

 dently the result of a high degree of specialization, but there 

 are others that cannot be thus explained. The specialization 

 evidently began in the skull, and there reached its greatest 

 development. The peculiar armature of the skull has a partial 

 parallel in the genus Phrynosoma among the recent lizards, 

 and Meiolania among the extinct turtles. A suggestion of 

 the parietal crest may be seen in the existing Chameleo, which 

 offers other points of resemblance in its skull and skeleton. 

 These features, however, indicate only a very remote affinity, 

 and it is among the Dinosaurs alone that this group can be 

 placed, as a distinct family, in the order Ornithopoda. 



The main characters which separate the Ceratopsidce from all 

 other known families of the Dinosauria are as follows : 



