WEALDEN DINOSAURS. 507 



to the ulnar end of the distal articulation (ib. n) is 7 inches, 6 lines ; from the lower 

 border of the spur-joint (o) to the same part {n) is 5^ inches. 



The proximal surface or 'head' (fig. \, p), for articulation with the humerus, is semi- 

 elliptical. The long diameter gives the breadth above quoted ; the short diameter, at the 

 middle of the ellipse, is 2 inches 4 hnes ; the truncate border or chord of the semi-ellipse 

 is toward the ulna. From the posterior two thirds of this border the articular surface for 

 the ulna (fig. 3, q) extends down, \\ inch, at right angles with the proximal surface. It 

 is flat and rough, semi-elliptic in shape. 



The proximal surface is almost flat, feebly undulate, with a linear roughness for 

 ligamentous union with the humerus ; it is continued at its fore part upon the ridge-like 

 prominence of the bone (fig. 3, r, r), which bends toward the ulna as it descends, 

 terminating 2j inches below the humeral surface ; this rough extension of the articular 

 surface is separated from the flatter ulnar surface by a deep, smooth pit (ib. s), big enough 

 to receive fiJie end of the thumb. Beneath this articular surface the radius contracts to 

 a breadtli of 2 inches 5 lines, and a thickness of I inch 3 lines ; and this subcompressed 

 form, flat or subconcave toward the ulna, convex on the opposite side, but irregularly so 

 on both sides, continues two thirds down the length of the shaft ; which, then, gains in 

 thickness and breadth, but especially and rapidly in the latter dimension by the extension 

 of the distal end beneath that of the ulna. 



The distal surface for articulation with the ulna commences about 9 inches from the 

 proximal end of the radius in a pointed form (fig. 1, t), which rapidly expands to a breadth 

 of 2 J inches. This part of the distal ulnar surface is parallel, lengthwise, with the non- 

 articular surface of the shaft of the radius, is almost flat or slightly convex and rough, and 

 might be regarded as representing a partial interosseous syndesmosis; it is continued, 

 however, at its lower broadest part into a smoother concavity upon the proximal side 

 (ib. u, v) of the distal extension of the radius, and this concavity receives part of the distal 

 convexity of the ulna (ib. 1-, /:'). The distal end of the radius is excavated by two con- 

 cavities for the carpal bones ; that (ib. w) for the hemispherical part of the scaphoid is the 

 deepest, and measures about an inch and a half in both transverse and fore and aft 

 diameters ; the shallower concavity (ib. x) for the convex part of the cuneiforme is con- 

 tinued into a slightly convex svu'face, extending to the apex of the distal extension ulnad 

 (w) of the radius. 



On the shaft of the radius may be noticed a rough, slightly prominent tuberosity (y)^ 

 about 15 lines by 12, at the hinder or anconal margin, commencing about 4 inches from 

 the proximal end. The shaft is not quite straight ; the anconal surface below the tuberosity 

 gains in thickness, and is slightly concave lengthwise; the thenal surface is thinner, and 

 slightly convex lengthwise. 



The exceptional feature of this radius is an oblong, irregularly flattened, rough 

 surface, as if caused Ijy fracture, occupying the radial aspect of the distal expansion {m, o) ; 

 consequently, opposite the surface above described for articulation with the ulna. To 



