OSTEOLOGY OF BIRDS 267 



a short distance into the latter. Above it the neural spines are 

 notched in front, and have an elevated, stumpy process behind. 



The ends of the shortened diapophyses of the first free caudal 

 are usually overlapped by the ilia, but in the next segment these 

 processes .are much longer, to be longer still in the third and fourth 

 vertebrae. In the. next two they again become shorter, to be en- 

 tirely abortive in the ultimate one. In all they are broad and 

 depressed. 



Chevron bones are freely articulated between the centra of the 

 last three or four vertebrae of the tail ; they are bifid in front and 

 grow gradually smaller as we proceed in that direction. 



The pygostyle is here of considerable size, being an irregular 

 quadrilateral figure, with its lower margin thickened, and all the 

 others thin and cultrate. 



Appendicular skeleton. Pectoral limb. When the skeleton of 

 the upper extremity is in a position of rest alongside the body, 

 we find that the humerus is somewhat longer than the bones of the 

 antibrachium, and the pinion also projects beyond them behind to 

 the full extent of the last phalanx of index digit. 



The humerus is characterized by a broad, proximal extremity, 

 showing an enormously deep pneumatic fossa, and a distinct trench 

 between the ulnar crest and articular head, running beneath the 

 latter. Its cylindrical shaft shows the usual sigmoid curve from 

 radial and anconal view. Nothing unusual marks its distal ex- 

 tremity, where we find the trochlear tubercles for radius and ulna. 



These latter bones are nonpneumatic, in common with the re- 

 mainder of the skeleton of this limb. The shaft of the radius is 

 straight, whereas it is curved in the ulna, the concavity occurring 

 on the side toward the interosseous space. 



The cylindrical shaft o»f this latter bone is faintly marked by a 

 double row of papillae for the secondaries. 



In the carpus we find the two usual segments of forms common 

 to the majority of the class. 



In the pinion the bones are all remarkably well developed. Carpo- 

 metacarpus has its main shaft straight and of a caliber intermediate 

 between those of the antibrachium or larger than the shaft of radius 

 and smaller than the "shaft of ulna. First metacarpal is short and 

 anchylosed in the usual manner to shaft of index. The long tri- 

 hedral pollex phalanx bears a distal joint, which is also the case 

 with the second phalanx of index digit. 



All the bones of the pelvic extremity are nonpneumatic, though 

 the principal long ones have sizable medullary cavities. 



