OSTEOLOGY OF BIRDS 3OI 



Now in Oidemia perspicillata I find structures quite 

 similar to this although the relations of the parts to each are 

 not a little different. The laryngeal box is symmetrical in form 

 and heartshaped, being, however, somewhat flattened behind, while 

 in front it is convex. It measures about 1.8 centimeters in its long- 

 est diameter, and exhibits a distinct longitudinal median crease 

 anteriorly, being unossified below on its posterior aspect. The 

 tracheal dilatation is very conspicuous, and *is not over 1.5 centi- 

 meters above the laryngeal box ; it is hollow ; subcircular in form 

 when viewed from in front ; convex anteriorly, flattened behind ; 

 thin in its walls, though they are unfenestrated anywhere ; com- 

 pressed from before, backward, having a vertical diameter of 2.2 

 centimeters, a transverse of 3, and an anteroposterior one of 

 about a centimeter at its thickest part. At present I know of no 

 other American duck that has this bulbous expansion upon the 

 trachea. 



APPENDICULAR SKELETON IN THE DUCKS 



Pectoral limb. In Spatula c 1 y p e a t a the humerus is per- 

 fectly pneumatic, and a large foramen is found at the usual site. 



The bone is considerably longer than the nonpneumatic ulna and 

 radius. Its radial crest is rather low and short, while the ulnar one 

 curls conspicuously over the pneumatic fossa. Between this latter 

 and the humeral head a deep notch, or rather groove, is found. 



The shaft is of a glistening whiteness, and composed of a wonder- 

 fully compact tissue, and shows scarcely any curve along its con- 

 tinuity. The distal extremity presents the usual characters, the 

 oblique and ulnar tubercles on the radial side and a broad passage 

 for the tendons on the other. 



Along the shaft of the ulna we notice a faintly pronounced row 

 of papillae for the secondary quill butts, a longitudinal muscular line 

 marking the opposite side. This bone is considerably bowed along 

 its proximal third, while, on the other hand, the radius is nearly 

 straight. The two carpal elements which remain free throughout 

 life in Aves generally are here present, and of a comparatively large 

 size. Ulnare in most ducks shows a strongly defined groove down 

 its anconal aspect for the lodgment of the tendon which there 

 passes. 



Carpometacarpus presents the usual form, and its main shaft is 

 n)ore than two thirds as long as the radius. There are two pha- 

 langes in pollex digit, as there are three in index, the blade of the 

 proximal joint of this latter finger being narrow and solid ; the 



