OSTEOLOGY OF BIRDS 327 



a centimeter longer than they are in the former, although in no way 

 increased in caliber. 



I have not s?en the radius in D e n d r o c y g n a a u t u m n a 1 i s , 

 as my specimen is not perfect to that extent, but an ulna in that 

 bird shows the olecranon process to be very well developed, with a 

 small pneumatic foramen immediately beyond it, toward its lower 

 aspect. Its shaft is handsomely bowed, while the single rozv of 

 papillae are not especially conspicuous. Ulnarc and radiate, the 

 two usual free carpal bones of the wrist, occur in all these birds, 

 and they present the characters most commonly seen in these seg- 

 nients throughout the Class Aves. 



The carpomctacarpiis in my specimen ofBranta canadensis 

 has a length of 10.8 centimeters, its proximal end being very power- 

 fully developed. Its main shaft is straight, being flattened at the 

 front, and at the sides. The medius metacarpal, nearly three fourths 

 less in bulk, is also flattened and slender. It extends somewhat 

 below the main shaft. Pollex metacarpal is very short; jutting out 

 obliquely from the proximal. end of the bone. Within this, upon 

 the anconal side of the head of the shaft, a large and prominently 

 distinct tubercle is seen, that is invariably present in all true Anseres. 

 An ample trochlea is formed by the os magnum, or rather that part 

 of the bone representing it, for the articulation with the carpal 

 segments. The proximal and expanded phalanx of index digit, has 

 a length of 4.5 centimeters, and is unperforated, though very thin, 

 at the center of its blade portion. The spikelike trihedral-shaped 

 free phalangeal (terminal") joints are large and long, the hinder 

 'border in the distal one being especially sharp ; while its extremity, 

 as well as that of the pollex digit, appears to be faceted for a free 

 claw. These are found in many ducks and geese, and I am in- 

 clined to believe they have been lost in the specimens now under 

 consideration, (Branta, Chen, Anser and Dendrocygna). The 

 general characters of the phalanges of manus agree in all of these 

 forms, and upon measurement I find the carpometacarpus of C h e n 

 h . nivalis to have a length of 8.8 centimeters, and the prox- 

 imal phalanx of index digit to be 4 centimeters long; in Anser 

 a 1 b i f r o n s the corresponding bones measure respectively in 

 length 8.4 centimeters and 3.6 centimeters; and in Dendro- 

 cygna autumnalis 5.5 centimeters and 2.4 centimeters. 



Pelvic limb. The bones of this extremity in Branta 

 canadensis are stout, of harmonious proportions, and power- 

 fully built. Femur, which has a length of about 9 centimeters has 



