7'4 



BULLETIN 



UNITED STATES NATIONAL MUSEUM. 



Fig. 39.— Outline of articulated proximal extremities 

 OF metacarpals of bight mantjs of Stegosaurus sulca- 

 Tus Marsh. Type. Cat. no. 4937, U.S.N.M. J n'at. size. 



Viewed from the front the proximal and distal ends are about evenly expanded 

 transversely, but the proximal greatly exceeds the distal in the lateral aspect. The 



constricted shaft of moderate breadth 

 when seen from the front is produced 

 backward, the sides being pinched to- 

 gether, fonning a stout ridge wliich 

 joins the two ends of the bone. The 

 posterior surface of this ridge especially 

 at its center is rugosely roughened. 



The distal end has two distinct ar- 

 ticular faces, which meet at an obtuse 

 angle on the distal end. The larger of 

 these is shallowly concave transversely 

 and convex vertically for articulation with the first phalanx. This articular surface 

 does not round up on the anterior surface of the bone as in the preceding meta- 

 carpals, but the two surfaces meet sharply 

 at right angles. This feature will be dis- 

 cussed later in connectioii with meta- 

 carpals IV and V. The second surface 

 mentioned above looks outward and 

 downward and was probably opposed by 

 an inwardly directed process from the 

 rV metacarpal as shown in 5, plate 21, 

 figure 2. 



Metacarpal IV has much the same 

 proportions as metacarpal II, except for 

 the heavier proximal end. The shaft is 

 constricted in both vertical and lateral 

 diameters. The ends are expanded, more 

 especially the distal, and particularly on 

 the inner side of this end. The articular 

 face for the first phalanx is flattened and 

 meets the anterior surface of the shaft at 

 right angles. This feature is even more 

 pronounced than in the preceding meta- 

 carpal. These siu-f aces would appear to 

 indicate the fiixed nat\u-e of the pha- 

 langes which opposed them, and, as will 

 be shown later, probably bore phalanges 

 which did not reach the outside of the 

 muscular mass of the foot. As in meta- 

 carpal III, on the outer side of the 

 distal end a second articular surface 

 looks downward and outward and was 

 probably closely connected to an inwardly directed process from the distal end 

 of metacarpal V. ^ 



Fig. 40.— Left fore foot of Stegosaurus stenops Maesh 



SHOWN AS found ARTICULATED. TYPE. CAT. NO. 4D34, 



U.S.N.M. >j NAT. SIZE. Palmar veew. r, Radule; rd, 



DISTAL END OF RADIUS; U, DISTAL END OF ULNA; Ul, 

 COALESCED INTERMEDIUM, ULNARE, AND PI.'^IFORM: II, V, 

 METACARPALS TWO AND FR^E. 



