OSTEOLOGY OF THE ARMORED DINOSAURIA. 



85 



Fibula (_/.).— -The fibula is slender, with the proximal end heavier than the distal. 

 The tibial side of the upper end is hollowed out in order to better conform to the 

 surface of the tibia, with which it articulates. An obtuse thickened ridge passes 

 diagonally across the inner surface, about 70 mm. below the proximal end, and 

 serves to distinguish the fibulae of Stegosaurus from those of other known dinosaurs. 

 The proximal articular surface is rounded and rugose and quite on a level with 

 that of the tibia. 



The surface next to the tibia is plain, while the opposite side is irregularly con- 

 vex. The distal end, much flattened and expanded antero-posteriorly, was closely 

 applied to the flattened surface of the tibia. 



A somewhat roughened area for muscular attachment passes diagonally across 

 the outer surface just above the center of the bone. The distal end when articu- 



-<z 



Fig. 48.— Distal end of eight tibia of Stegosaurus sp. Cat. no. 7387 U.S.N.M. 1 NAT. size, a, external border, 

 6. anterior border; /, surface for fibula. Dotted line shows position of astragalus when articulated. 



lated rests upon the very small calcaneum. In some individuals it has been found 

 to coalesce with the calcaneum, these in turn with the astragalus and tibia, forming 

 a smooth convex articulation for the ankle joint. The principal features of the 

 fibula are shown in figures 47 and plate 25, fig. 5. 



Measurements of fibulae. 





S. stenops. 

 Type. 



Stegosaurus sp. 



No. 4934. 



No. 7389. 



No. 7380. 



No. 7390. 



No. 6644. 



No. 73S4. 





mm. 

 610 

 109 



74 



mm. 



515 



78 



90 



38 



mm. 



518 



81 



79 



38 



mm. 

 548 

 71 

 68 

 47 



mm. 



579 



S2 



99 



38 



mm. 



550 



72 



95 



41 













51873°— Bull. 89—14- 



