BIRDS. 221 



piece with the haunch-bones. The sternum is greatly ex- 

 panded, and, in the size of its mesial crest and division of 

 its posterior extremity, furnishes several characteristic 

 marks of species or genera. The vertebral extremity of 

 the ribs is bifurcated, the sternal end has an osseous ap- 

 pendix, and on the middle, there is a flat process project- 

 ing obliquely backwards over the succeeding rib. The 

 clavicles are united to the anterior edge of the sternum, 

 where they are received into an oblique groove. The sca- 

 pular extremities of the clavicles are kept asunder by the 

 merry-thought, which forms the porch as it were to the 

 thorax. The scapular bones are long and narrow. The 

 humerus is articulated with the scapula and clavicle in a 

 shallow cavity. The ulna which supports the secondary 

 quills, has, in many species, a row of tubercles on its dor- 

 sal aspect. The radius is slender. The carpal bones 

 are small, and two in number. The metacarpal bone con- 

 sists of two branches united at each extremity. On its an- 

 terior edge, near its base, the thumb bone is situated, which 

 supports the bastard wing. This bone, in many birds, as 

 the water-rail, land-rail, and arctic gull, supports, at its ex- 

 tremity, a nail or claw, more or less obvious externally. 

 At the extremity of the metacarpus, there are two fingers, 

 the largest of which consists of two phalanges, the smallest 

 of one styloid phalanx. 



The pelvis of birds is imperfectly developed ; the ossa in- 

 nominata, lumbar vertebras, and sacrum, form only one 

 bone, open ventrally where the symphysis pubis occurs in 

 quadrupeds. The former is short, and does not appear ex- 

 ternally. The tibia (usually, but improperly, termed the 

 thigh,) is perfect ; the fibula is ossified to its femoral extre- 

 mity, and never reaches its whole length. The tarsus (im- 

 properly termed the leg,) is trifid at its lower extremity 

 for the articulation of the phalanges of the three toes. The 



