170 O. C. Marsh—American Jurassic Dinosaurs. 
Tue Fore Limes. 
The principal bones in the scapular arch and fore leg of 
Stegosaurus were described and figured in the article already 
cited. In Plate VIII, figure 1, these are brought together, and 
the fore foot added in its natural position. The humerus an 
bones of the fore arm show clearly that this limb, although 
very small in proportion to the hind leg, was very powerful, 
and as it admitted of considerable rotation, it was doubtless 
used mainly for other purposes than locomotion. The foot 
here represented was found by the writer, with the bones 
nearly in the position indicated. There are only three carpal 
bones in the proximal series, and in this foot the distal segment 
of the carpus remained unossified. There are five digits, the 
fifth being the smallest. 
The great disproportion in size between the fore and hind 
limbs, as well as the structure of the principal joints in each, 
show plainly that Stegosaurus walked mainly as a biped. The 
massive posterior limbs, and the huge tail doubtless formed a 
tripod on which the animal rested at times, while the fore 
limbs were used for prehension, or defense. The heavy der- 
mal plates and powerful spines probably rendered the latter 
an easy task. 
Yale College, New Haven, Jan. 24th, 1881. 
