THE PECTORAL GIRDLE. 31) 



least as a rudiment of the aeromion, /. >/.. -yina scajjit/ae. The upper 

 dorsal process evidently represents a rudimentary processus coracoi- 

 ffeii*. The anterior border (Fig. 28 a) is free, somewhat sharp, and 

 slightly concave; the posterior (Fig. 28 p), also concave, is free 

 externally ; while internally, where the division of the ventral border 

 commences, it takes part in the formation of the articular cavity of 

 the shoulder (Figs. 28 and 29 c.a.). 



Articulation with tie * up rased pit fa. The scapula consists of 

 a shell of compact bony tissue and an inner portion of cancellous 

 tissue ; this latter passes, at the boundary between this bone and the 

 suprascapula, through an intermediate layer of calcified cartilage, 

 which is directly continuous with the cartilage of the suprascapula. 

 The compact superficial layer ceases where the calcified cartilage 

 begins, and the periosteum of the scapula passes directly into the 

 perichondrium of the supraseapula. 



2. The ventral portion of the shoulder-girdle consists of three 

 parts, which lie one behind the other. 



a. The larger and posterior bone, the coracoid (Figs. 24 co, 30), 

 is contracted in the middle, and expanded 



at either end, especially at the sternal end. 

 The inner half is flattened from above down- 

 wards; externally it becomes more cylindrical. 

 The anterior and posterior borders are markedly 

 concave; the outer border (Fig. 30 /) ar- 

 ticulates by means of a cartilage with the 

 jimc. forai.-nuh'vs of the scapula ; the inner bor- 

 der (;#) is separated from its fellow of the 

 opposite side bv the epicoracoids. This inner 



1 L " * ., . Left coracuid twice nat. 



border is so broad, that it almost touches the ze. 



inner end of the clavicle (Fig. 24 r/.). A " Frombeiow. 



, , ' '- From behind. 



coracoid foramen is thus formed between the / outer extremity. 



i -i MI / 7 f .1 i/i Innei extremit\ 



t\vf! bones, similar to the foramen ovate or the 

 pelvis. 



b. The small anterior bones of the ventral portion of the shoulder- 

 girdle (Fiu's. 24 cL, 31), I, like Cuvier and F'g- 3'- 

 others, regard as clavicles. Duges (n. 33) 



names them ' aeroi/iiaL' Each bone is nar- 

 rower than the coracoid, smaller internallv 



Clavicle of the left side, 



(/), broader externally (/). and articulates by twice nat. size. 



\ / , , i " i -i .,1 l Outer eitreniity. 



this broader end with the cartilage uniting the IN inner extremity. 



