62 PROFESSOE OWEN ON THE 



substance of the sternum gradually increases in thickness from the sharp lateral margins 

 to the middle, above the base of the keel, and shows there a fine pneumocancellous 

 texture (PI. XXIII. fig. 4). 



§ G. Scapular Arch. (Plates XV. & XX.) 

 This consists of the scapula (PI. XX. figs. 6, 7, 8 & 9, si), coracoid (ib. figs. 4 & 5, ii), and 

 clavicle (ib. ss), the latter ending in a point and here tied by ligament to its fellow, to form 

 a furculum. I have received the elements of this arch in three conditions : — one in which 

 the bones, though of full size, are separate ; a second, in which the scapula and coracoid 

 are confiuent, but the clavicle distinct ; a third, in which the three bones are confluent 

 at the ends converging to the humeral articulation. The scapula (ib. figs. 6 & 7, 8 & 9, 

 .^l), 3 inches 7 or 8 lines in length, has the usual sabre-shaped body, slightly expanding 

 and decurved at its free extremity, the breadth of which is 7 lines : it terminates ob- 

 tusely : varieties of shape are shown in figures 6 & 8. The outer surface of the bone, 

 at the two posterior thirds of its extent, is slightly concave and marked by muscular 

 attachments ; the inner surface of that part is smooth and slightly convex : the bone 

 increases in breadth, with some diminution of thickness, towards the articular end, and 

 is remarkable for sending off from the lower border, at 7 or 8 lines from that end, 

 a short process (ib. 5i) ; between this process and the articulation the breadth of the 

 bone is little more than -S lines ; the breadth of the articular end is 9 lines. Nearly 

 one-half of it is occupied by the almost flat, subcircular humeral surface (fig. 8, a), \vith 

 a diameter of 4^ lines, and directed upward, outward, and a little forward. From this is 

 continued an oblong, much narrower coracoidal surface, beyond which the acromial pro- 

 cess (fig. 6, c) extends forward, curving toward the coracoid, and terminating obtusely. 



The coracoid (ib. figs. 4, 5, 8 & 9, 62), averaging a length of 3 inches 7 lines, expands 

 to a breadth of 1 inch .5 lines at its sternal end (52), of which the articular surface (e) 

 occupies an inch ; the non-articular part forms the outer angle (m), and extends in advance 

 of the pneumatic foramen (PI. XVI. fig. 4, j>) at that part of the breast-bone: the outer 

 border which extends from this free angle to the body of the bone, into which it subsides, 

 at one-third of the extent of the bone, is sharp ; the inner border is obtuse to near the 

 inner angle (PI. XX. figs. 4 & 5, n). The outer surface of the expanded sternal end 

 is smooth and convex ; the inner surface is flatter and more irregular, perforated by 

 pneumatic foramina ; the diameter of the subcylindrical part of the shaft is 4 lines : the 

 extremes of diff'erence in the distal expansion of the coracoid are shown in figs. 4 & 8, 

 52, PI. XX. A muscular ridge and rough surface (ib. fig. 9, r) mark the back part 

 below the middle of the shaft. The bone then expands to its upper articular end, 

 which is obliquely truncate from within outward : it shows, first, the oblong surface 

 for the scapula, which is extended upon the inner prominence of that end ; next, the 

 larger and full oval surface for the humerus (/*), from which the thick, obtuse, inner 

 'continuation of the scapular end projects inward, forward, with a slightly upward curve. 



