The Skeleton 81 
the cartilaginous sternum proper (2), the xiphi- 
sternal horns (5), and the bony episternum or inter- 
clavicle (1). The latter is an elongated, flattened 
bone of somewhat spatulate outline, lying in the 
midventral line; it projects forwards to about the 
sixth cervical vertebra, while the anterior edge of 
the sternum is below the eighth cervical. Lying 
dorsal and lateral to the episternum is the flat, 
almost membranous sternum, to the posterior 
border of which the first two thoracic ribs are 
attached. The xiphisternum consists of two long, 
slender rods of cartilage; the anterior ends of these 
rods are in contact with each other and with the 
posterior border of the sternum; from this point 
they gradually diverge from each other as they 
extend caudad. A membrane extends between 
the horns as far back as the attachment of the last 
thoracic ribs. 
IV. The Appendicular Skeleton. 
The Pectoral Girdle and Anterior Limb. The 
pectoral girdle (Fig. 27) is of a very simple type, 
consisting, unless the episternum (interclavicle) 
be counted, of but two bones, the scapula (s) and 
coracoid (c). The former consists of an upper, flat, 
paddle-shaped portion and a thicker lower portion 
which articulates anteriorly with the coracoid, and 
posteriorly forms about half of the notch-like 
glenoid cavity. The dorsal edge of the flattened 
portion is continued as a small, cartilaginous supra- 
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