THE RIBS. 



[CHAP. 



of 



great Anteater 16, the Cape Anteater (Orycteropus) i; 

 which the last is sometimes very short. 



The MARSUPIALIA have nearly always 13 pairs of ribs : 

 the Koala (Phascolarctos) with but n, and the common 

 Wombat (Phascolomys vombatus] with 15, being the only 

 known exceptions. The sternal ribs are articulated by 

 synovial joints with the sternum, but are not distinctly 

 segmented from the vertebral ribs, and are but feebly 



O ' - 1 



ossified by endostosis. There are no intermediate ribs. 



FIG. 45. Sternum and ribs of the Great Armadillo (Priodou gigas), \. 

 ps presternum ; xs xiphisternum. 



In the MONOTREMATA the intermediate ribs are well 

 marked (see Fig. 44, p. 105), and only partly ossified by 

 endostosis, while the sternal ribs (except the first) are, 

 according to Parker, strongly ossified ectosteally, as in Birds. 



