The Skeleton 8i 



the cartilaginous sternum proper (2), the xiphi- 

 sternal horns (5), and the bony epistemum or inter- 

 clavicle (i). 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 epistemum is the flat, 

 almost membranous sternum, to the posterior 

 border of which the first two thoracic ribs are 

 attached. The xiphistemum 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. 2^) is of a very simple type, 

 consisting, unless the epistemum (interclavicle) 

 be counted, of but two bones, the scapida (5) 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- 



