248 THE SHOULDER GIRDLE. [CHAP. 



(af), between the coracoid border and the spine, called, in 

 works on human anatomy, "supraspinous fossa;" (2) the 

 postscapular fossa (pf\ between the glenoid border and the 

 spine, also called " infraspinous fossa ; " and (3) the sub- 

 scapular fossa, between the coracoid and glenoid borders 

 on the side of the scapula opposite to the spine. 



The greater part of the scapula is ossified by ectostosis (as 

 the shaft of a long bone) from a single centre, which is 

 placed not far from the middle of the bone ; but this ossifi- 

 cation does not extend into a certain portion near the 

 superior (or dorsal) extremity. This part (suprascapula 

 of Gegenbaur) either remains cartilaginous or " is feebly 

 ossified by one or more endosteal patches, or by the creeping 

 upwards of such deposit from within the main bone " 

 (Parker). When the spine runs out into a projecting 

 acromial process, more or less of its terminal portion is 

 ossified separately as an epiphysis. 



The coracoid always ossifies from one or more separate 

 centres, and remains for some time suturally connected 

 with the scapula, though firmly ankylosing with it by the 

 time the animal has attained maturity. Sometimes (as in 

 the Sloths) it forms a considerable part of the glenoid fossa ; 

 sometimes (as in most Carnivora and Ungulata) it is a mere 

 nodule, which becomes blended with the anterior margin of 

 the fossa. 



In the Ornithodelphia (see Fig. 84), as in Birds and Rep- 

 tiles, the coracoid is largely developed, and articulates with 

 the presternum, and there is in addition a plate of bone in 

 relation with its ventral edge called epicoracoid. A small 

 plate of cartilage or bone, often found attached to the side 

 of the presternum in certain Rodents and Insectivores, is 

 considered by Parker as representing the epicoracoid of 

 the Ornithodelphia, and by Gegenbaur as the sternal ex- 



