154 



DINOSAURS OP" NORTH AMERICA. 



that now many of the more important characters of the group can he 

 determined with certainty. 



FORE AND HIND LIMBS. 



In its present condition the specimen shows both the fore and hind 

 limbs in good preservation, portions of the scapular arch, and appar- 

 ently the entire pelvis and sacrum, various vertebra?, ribs, and other 

 parts of the skeleton. It is doubtful if any portions of the skull are 

 sufficiently well preserved for determination. On PL VI are given out- 

 line restorations of the fore and hind limbs of this specimen. 



The scapula is of moderate length, and its upper portion broad and 

 thin. The humerus is slender, with a strong radial crest. The shaft is 

 very hollow, with thin walls, and the cavity extends almost to the distal 

 end. The latter is but little expanded transversely. The radius and 

 ulna are short, and were closely applied to each other. There were but 

 four di 

 slender. 



S its in the maims, the first being short and stout, and the others 



Fin. 3.— Left leg and foot of Hallopun victor Marsh; side view. Natural size. 



a, astragalus i c calc mm; d, tarsal; /, femur; t, tibia; //, second metatarsal; V, remnant of fifth 



metatarsal. 



All three pelvic bones aided in forming the acetabulum, as iu typical 

 dinosaurs. The ilia are of the carnivorous type, and resemble in form 

 those of Megalosaurus. The pubes are rod-like, and projected down- 

 ward and forward. The distal ends are closely applied to each other, 

 but not materially expanded, and in the present specimen are not 

 coossilied with each other. The ischia projected downward and back- 

 ward, and their distal extremities are expanded, somewhat as in the 

 Crocodilia. 



The femur is comparatively short, with the shaft curved and very 

 hollow. The tibia is nearly straight, much longer than the femur, and 

 its shaft equally hollow. The fibula was slender and complete, but 

 tapered much from above downward. Its position was not in front of 

 the tibia, as in all known dinosaurs, but its lower extremity was out- 

 side, and apparently somewhat behind, the tibia. 



The astragalus is large, and covered the entire end of the tibia, but 

 was not coossifled with it. The calcaneum is compressed transversely, 



