No. 4.] SHUFELDT OX THE OSTEOLOGY OF SPEOTYTO. lO'J 



Of the upper extremity. — ^The upper extremity consists of ten distinct 

 bones in the full-grown bird, omitting minute sesamoids that might ex- 

 ist. These are the humerus of the arm, the radius and ulua of the fore- 

 arm, two free carpals, the metacarpal, and four phalanges. (See PI. I.) 

 The humerus is a long, extremely light, and smooth bone, and when 

 viewed from above in its position of rest, with the wing closed, it re- 

 miuds one of the curve in the small italic letter/, being concave above 

 towards the scapula ; and this bone is so twisted that this same curve 

 is exhibited, though not quite as well marked, when viewing it laterally. 

 The humerus is 5.5 centimetres long, subcylindrical on section at mid- 

 shaft, at which point a minute aperture exists for the passage of the 

 nutrient vessels that are distributed to the osseous tissue and its inter- 

 nal lining. This foramen enters the bone very obliquely, its external 

 orifice being the nearest the proximate extremity. This end is well ex- 

 panded and surmounted above by a strongly developed radial crest that 

 overhangs the shaft slightly towards the palmar aspect. It occupies a 

 line on the bone from the articular facet for the shoulder -joint to an 

 extent shown in PI. I. The ulnar crest, or lesser tuberosity, encloses 

 quite an extensive fossa below, which acts also as a partial screen to the 

 pneumatic foramina, for the humerus is highly pneumatic. They usually 

 consist of one circular opening, surrounded by a group of many smaller 

 ones. In young birds a very large foramen is generally present ; this 

 closes in as age advances. Between the two tuberosities is the vertical 

 and elliptical convex facet for articulation with the glenoid cavity of the 

 shoulder-joint, constituting the " head of the humerus ". The radial crest 

 displays palmad, a ridge for the insertion of the tendon of the pectoralis 

 major. The distal end of the humerus is also expanded in the vertical 

 plane and gently convex anconad, the reverse condition of the proximal 

 extremitj^. It jjresents, for examination, the articular facets for the 

 giuglymoid joint it forms with radius and ulna, and the superior and 

 inferior condyles. The larger, and at the same time the superior, of these 

 two facets is intended for the cup-shaped depression in the head of the 

 radius, as well as a portion of the articular surface on the ulna. It is 

 ovoid in form and placed obliquely on the bone, the inferior end of the 

 long axis of the oval being situated the nearer the proximal extremity 

 of the shaft. This fiicet is separated from the trochlea surface for the 

 ulna by a well-marked depression ; this latter is a knob-like tubercle 

 when compared with the radial facet. The condyles and the entire ar- 

 ticular surface are about in the same plane posteriorly; that is, neither 

 increases the length of the bone, one more than another. Passing from 

 the trochlea surface for the ulna towards the inner aspect of the shaft, there 

 is to be observed a shallow depression, which corresponds to the olecra- 

 non fossa of human osteology, and in full extension of the limb allows 

 room for that process of the ulna in this bird. The radius has an average 

 length of G.G centimetres, and the ulna a corresponding length of 6.8- 

 centimetres, so that their distal extremities, when articulated, as we ex 



