1Iatciii:r: I-oki'. Limi; anh M \\i^ oi r.KONTOSAL'Rus. 3()7 



with the description given by Usboni and (i ranger of the supposed 

 scaphodunar in I)ii)lodocus, and with those authors I agree in making 

 it homologous with tiiat element in the mammalian carpus. If my 

 interpretation of the position of this bone in the manus is correct the 

 following description of this element would apply. The general form 

 is that of a circular disc, thin in front l)ut considerably thickened 

 posteriorly. The superior surface is crossed antero-posteriorly by a 

 low, broad ridge which divides it into two slightly concave and sub- 

 equal surfaces, the larger and smoother of which was for articulation 

 with the external half of the distal end of the radius, while the 

 smaller and more rugose surface articulated with the internal portion 

 of the distal articular surface of the ulna. Inferiorly this bone pre- 

 sents a gentle convex, polished, but corrugated surface for articulation 

 with metacarpals II., III. and IV. No other carpals were found with 

 or near this foot, and after a careful study 

 of it and the articular surfaces of the 

 distal ends of the radius and ulna and 

 considering the position in which nieta- 

 carjials II., III. and IV. lay with refer- 

 ence to these bones and metacarpals!., ^'^- '°- Right scapho- 



j ,, , . , -»-ri' 1 lunar front view seen obliquely 



and \., as shown in i)laies XIX. and , , , / , 



' from above, about one- fourth 



XX., it appears quite probable that it natural size. (No. 563.) 

 was the only ossified element i)resent in 



the carpus of Brontosaurus and therefore that the Brontosaur carpus, 

 like the tarsus, consisted of a single element. An oblique front view 

 of this bone is shown in Fig. 10. 



T/ie Metacarpals. — All the elements of the metacarpus were present 

 and in approximately their normal positions when the foot was uncov- 

 ered, as shown in plates XIX. and XX. 



Metacarpal I. is short and much the strongest bone of the entire 

 series. The proximal end is very deep, but much compressed. The 

 articular surface is gently concave vertically and convex transversely. 

 The internal lateral margin of the proximal end is regularly convex 

 so that this margin and the proximal articular surface as well conform 



