marsh.] STEGOSAURUS. 191 



The pubic element of the pelvis of Stegosaurus ungulatus is in general 

 form somewhat like that of Camptosaurus. The prepubis consists of 

 a strong spatulate process, projecting forward nearly horizontally. Its 

 proximal end articulates with the preacetabular process of the ilium. 

 The postpubic branch extends backward and downward, nearly to the 

 end of the ischium. The two bones fit closely together in this region. 

 The usual pubic foramen is in this species replaced by a notch, opening 

 into the acetabular cavity. In a smaller species, Stegosaurus affinis, 

 the postpubic bone is slender and more rod-like, not flattened as in the 

 specimen here figured. 



THE FORE LIMBS. 



On PI. XLVII some of the bones of the scapular arch and anterior 

 limbs of Stegosaurus are figured. The scapula and coracoid are of the 

 true dinosaurian type. The former has its upper portion rather short 

 and moderately expanded. The coracoid was closely united to the 

 scapula by cartilage. It is perforated by the usual foramen, which in 

 some cases may become a notch. 



The humerus (fig. 3) is short and massive. It has a distinct head 

 and a strong radial crest. The shaft is constricted medially, and is 

 without any medullary cavity. The ulna (fig. 4) is also massive, and 

 has a very large olecraual process. Its distal end is comparatively 

 small. The radius is smaller than the ulna. The fore limb, as a whole, 

 was very powerful aud adapted to varied movements. There were 

 five well-developed digits in the fore foot, as shown on PI. XLVIII, 

 fig.l. 



THE HIND LIMBS. 



The femur of Stegosaurus (PI. XLVII, fig. 1) is by far the largest 

 bone in the skeleton. It is remarkably long and slender. There is no 

 distinct head, and the great trochanter is nearly or quite obsolete. The 

 shaft is of nearly uniform width and very straight. There is no evi- 

 dence of a third trochanter. The distal end of the femur is peculiar 

 in having very flat condyles, with only a shallow depression between 

 them. The external one has only a rudiment of the ridge which passes 

 between the heads of the tibia and fibula, aud is very characteristic of 

 true dinosaurs and birds. 



The tibia (fig. 2) is very much shorter than the femur. Its superior 

 end is unusually flat, indicating that it met the condyles of the femur 

 so as to bring the two bones at times nearly or quite into the same 

 line. The shaft of the tibia is constricted medially, leaving a wide 

 space between it and the fibula. The distal end of the tibia is blended 

 entirely with the convex astragalus, so as to resemble strongly the cor- 

 responding part in birds. 



The fibula (fig. 2) is slender, and has its smaller end above. This 

 extremity is applied closely to the head of the tibia by a rugose suture, 

 so as to unite readily with it. Its upper articular surface is nearly or 

 quite on a level with that of the tibia. The distal end of the fibula is 



