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lower sides, or costae, are straight. Tlie outer surface presents two wide and 

 shallow concavities separated by a slighter median convexity giving origin to 

 the spine : the inner side has its undulations reversed, presenting two con- 

 vexities divided by a median concavity. The spine of the scapula thus bisects, 

 nearly equally, the outer surface of the bone, commencing at the middle of the 

 base, having its origin extended in nearly a straight Une to within an inch and 

 a half of the glenoid cavity, and progressively increasing in height as it ap- 

 proaches this termination. The free margin of the spine begins to expand a few 

 inches from its posterior origin, and progressively increases in breadth, forming 

 thus a rough flattened plate, overhanging chiefly the supraspinal fossa, until it 

 quits the supporting spine, and inclines, as acromion, obliquely forwards and 

 downwards to join the flattened coracoid. This process reciprocally bends from 

 the anterior angle of the scapula towards the acromion, and forms, by its junc- 

 tion with it, a broad flattened bridge of bone, arching over the anterior outlet of 

 the supraspinal fossa. The articular cavity for the clavicle, of a transversely 

 elliptical form, is situated on a thickened part of the anterior margin of this 

 bridge, near the coracoid angle of the scapula. The supraspinal fossa is more 

 capacious at its anterior half than the inferior one ; it is perforated, a little ob- 

 liquely, by a circular aperture, one inch in diameter, midway between the an- 

 terior margin of the spine and the superior costa: this aperture, which represents 

 the supraspinal notch in other Mammalia, has its anterior margin broken by an 

 oblique groove, from which a shallow channel may be traced downwards to the 

 neck of the scapula. The anterior moiety of the superior costa is thickened, 

 inclined outwards, and gradually increases in breadth as it bends along with the 

 coracoid to be lost in the acromion. Ridges of bone traverse the wide supra- 

 spinal fossa in the direction towards its outlet, and indicate the fasciculi of the 

 powerful muscle which once occupied that cavity. The surface of the infra- 

 spinal fossa is similarly broken by ridges of bone, not more developed than those 

 above the spine. The straight inferior costa is not thickened : but on the inner 

 surface of the scapula, a broad and strong ridge of bone, commencing at the 

 posterior inferior angle, extends forwards, for some inches, so close to the in- 

 ferior costa, as to seem part of it ; it recedes from the costa as it advances for- 

 wards and gradually subsides in the lower convexity of the subscapular surface. 

 Besides the three principal undulations of this surface, which upon the whole is 



