OF BAL^XOPTERA MUSCULUS. 223 



Humerus. — This is a very heavy and solid bone, presenting a broad shaft, a globular 

 head and a tuberosity. On its outer surface the shaft is roughened, except toward the up- 

 per and posterior part. A little above the middle there is a considerable depression. The 

 inner aspect presents nothing noteworthj'. The posterior side is concave ; the anterior is 

 straight. The inferior surface is articular for the radius and ulna. It consists of two parts 

 which meet a little back of the middle in a transverse ridge. The posterior portion, which 

 is for the ulna, does not end on the inferior surface of the humerus, but passes up on to its 

 hinder sur&ce. If the bone be held vertically the globular head (PL vi, fig. 11 a) pro- 

 jects upward, outward and a little backward. On the inner superior aspect it presents a 

 large depression, from the front of which an ill-defined groove runs downward and outward, 

 corresponding to the "anatomical neck" of human anatomy. From the front of this groove 

 a large and rough tuberosity projects forward and slightly inward. (PI. vi, fig. 11 6.) 



MEASUREMENTS. 



Length 14.62 in. 



Breadth through head and tuberosity . ......... 9.25 " 



" " about middle of shaft 6.75 " 



" " lower end 8.25 " 



Thickness through middle of shaft 4.25 " 



Radius. — This bone consists of little besides the shaft. Its anterior border is very 

 slightly convex ; the posterior rather more than correspondingly concave. The posterior 

 border is thickened at the two ends where it joins the ulna. The anterior border ends 

 above in a small prominence directed forward. On the posterior border there is a large nu- 

 trient foramen directed upward. 



It should be remarked that the inferior epiphyses which were detached from the radii 

 and ulniie were very largely cartilaginous, and as only the ossified parts have been retained 

 and replaced, the bones lose something in length. 



MEASURE MENTS. 



Length 23.37 in. 



Breadth at upper end 6. " 



" about middle 4.37 " 



" lower end 5.87 " 



Thickness at about middle 2.25 " 



Ulna. — This is a much more delicate bone than the radius. The edges are more 

 curved — the posterior most of all. The anterior edge expands very much in the upper 

 third of the bone. The superior epiphysis forms the articular plate for the inferior surface 

 of the humerus. The olecranon projects backward fi'oni about the upper fifth of the bone, 

 and reaches upward so as to fit on to the humerus behind ; this part, however, is rough, 

 unlike the rest of the joint. The posterior border of the olecranon is convex ; its lower 

 portion very rough. The ulna is expanded at the lower end, where the outer surfixce is 

 very smooth. 



Length (exclusive of olecranon) • . . . . 22.62 in. 



Length of projecting part of olecranon o " 



Breadth at upper end through olecranon 6.75 " 



" " about middle 2.87 " 



" " lower end 5.12 " 



Thickness at about middle 2 " 



Length of olecranon (following curve) 8.75 " 



" " " (in straight line) 7.37 '• 



