Xo. 535] 



THE SAUROPODOl'S DLXOS.IUKS 



405 



cal position, with the deltoid border directed outward, 

 the opposite border inward, and the primitively dorsal 

 surface directed forward. This leaves the inner, prob 

 ably lesser, tuberosity projecting far within the inner 

 surface of the shoulder girdle. An examination of a lot 

 of mounted skeletons will show that in all mammals that 

 walk by moving the limbs in sagittal planes the inner 

 tuberosity is greatly reduced and removed to a position 

 in front of the head of the bone, and little or none of the 

 humerus projects beyond the inner surface of the scap- 

 ula. In two mammals I find a large process which cor- 

 responds, in position at least, to the inner one of the 

 sauropods. These are the echidna and the duck-bill, and 

 both of these mammals move the legs as the creeping 

 reptiles do. I believe that the prevailing manner of 

 articulating the humerus of the sauropods is wrong. It 

 ought to be placed in a plane approximately horizontal, 

 with the lower and upper faces in their primitive posi- 

 tions, with the deltoid border forward, and, when the leg 

 is in a median position of its swing, with the thickening 

 of the proximal articulately surface in contact with that 



ridge that passes across the scapula. In case the leg is 

 placed further forward or further backward, correspond- 

 ing parts of the convex articular end of the humerus 

 ought to pass under this ridge. There was no need at 

 any time of life that the lesser tuberosity should project 

 against the ribs or into the muscles. The arrangement 

 that I have described is that which may be observed in 

 the crocodile also. 



If now the ulna and the radius are articulated prop- 

 erly with the humerus the whole leg will function as it 

 does in the lizard and the crocodile. In the U. S. Na- 

 tional Museum is a specimen, shown me bv Mr. Chas. 

 W. Gilmore, which consists of the radius and the ulna, 

 somewhat crushed, but preserving nearly their original 

 relations to each other. These bones differ somewhat 

 from those of the crocodile, as might be expected. The 



