74 



NEW YORK STATE MUSEUM 



tuberosity. Bending over toward the palmar aspect of the bone 

 we observe a prominent radial crest. This extends from the upper 

 end of the articular tuberosity, 3 centimeters down the shaft. In 

 form it is a long isosceles triangle, with the angle above, and the 

 base on the shaft (the bone being alongside the body of the bird in 

 a position of rest, the one it occupies as I describe it). Viewed 

 from above in this position, the humerus has the usual long / form. 

 Smooth and cylindrical, the middle third of the shaft presents noth- 

 ing of special interest. Distally, it dilates as usual to support on its 

 palmar aspect the radial and ulnar tubercles; a muscular tuberosity 

 occurs above each of these for tendinal insertion. A broad, deep 

 valley is behind the oblique and ulnar tubercle occupying the an- 

 conal and distal extremity of the bone, to guide the passage of ten- 

 dons to the antibrachium. 



The radius of Circus has a length of 11 centimeters, being a 

 slender and nearly straight bone. Its head presents an elliptical, 

 concave facet for the oblique tubercle of the humerus, of consider- 

 able size, while the facet for the ulna about its head is not so exten- 

 sive. Just below this latter is the tuberosity for muscular insertion. 



The distal end of the radius is somewhat expanded transversely, 

 to allow room for the grooves for the passage of the tendons, and 

 a small articulation for the base of the os prominens. Below occurs 

 the usual facet for the radial e. 



The olecranon of the ulna is fairly well marked as a rounded 

 tuberosity, extending some two or three millimeters beyond the cir- 

 cular and concave facet intended for the ulnar tubercle of the 

 humerus. It also has the usual articular concavities for the oblique 

 tubercle and the head of the radius. The shaft of- the bone is 

 nearly four times the bulk of the shaft of the radius in caliber ; it is 

 cylindrical and but slightly curved; showing only very faintly the 

 row of papillae for the quill-butts of the secondaries, adown its 

 length. 



Nothing of marked importance presents itself for our examination 

 at the distal extremity of the ulna of Circus. The bone has here the 

 usual articular surfaces and tuberosities for radiale and ulnare. 

 Several years ago I described an ossicle of the antibrachium as it is 

 found in Circus, and named it the os prominens. In that article I 

 present a cut showing its relations to the neighboring bones and the 

 insertion of the extensor patagii lo'ngus. It is a small bone that 

 articulates with the radiale and distal end of radius. This ossicle 

 had previously been noticed by Prof. A. Milne Edwards, in a 

 kestrel in his Essai sur Apparcil Locomotcur des Oiscaux. Mivart 



