56 THE ROYAL SOCIETY OF CANADA 



bone was badly mashed along the edge. The head is strong and 

 rounded and is extended downwards as a pronounced ridge on the 

 posterior side of the bone. On the proximal end there is no depression 

 between the head and the inner tuberosity. 



Immediately below the radial crest the shaft is evenly elliptical 

 but expands distally with a pronounced concavity, both anterior and 

 posterior, continuing to the depression between the condyles. Both 

 the external and internal faces of the distal end of the bone are con- 

 spicuously flattened above the condylar facettes. The facettes are 

 strongly convex and sub-triangular in outline. 



Measurements of Humerus mm. 



Length 630 



Maximum thickness at proximal end 165 



Maximum thickness at distal end 130 



Minimum girth of shaft below radial crest 214 



Thickness of head 78 



Thickness at inner tuberosity 41 



Inner condyle, width antero-post 82 



Inner condyle, transversely 50 



Outer condyle, width antero-post 80 



Outer condyle, at right angles to above 52 



Maximum width at radial crest (?) 125 



The bones of the fore arm (Figs. 8 and 9) are similar in position 

 and shape to those of other trachodonts. The relative length of these 

 bones and that of the humerus is commonly regarded as a feature of 

 generic value. In this case the ulna, over the olecranon process, 

 is slightly shorter than the humerus, and the radius is considerably 

 shorter; this condition maintains in Trachodon and Hadrosaurus; the 

 radius and humerus are of equal length in Saurolophus; and in Hypa- 

 crosaurus the radius is much the larger bone. 



The ulna is a shaft-like bone expanded proximally in two direc- 

 tions making the articular aspect L-shaped. There is a strong ole- 

 cranon process. The distal end of the bone is but little expanded, 

 narrow anteriorly and wider posteriorly, with a median concavity. 



Measurements of Ulna mm. 



Total length over olecranon process (2 feet). 610 



Length between articular surfaces 574 



Greatest width of transverse expansion 104 



Greatest width of antero-post expansion 75 



Girth of shaft at midlength 158 



Maximum thickness of distal end 80 



