AXIAL SKELETON OP THE STEUTHIONID^. 



25 



The first sternal rib is rather shorter than the second vertebral rib, and is rather 

 more slender and cuiTed than ia Struthio or Ehea. The two distal articular surfaces 

 are blended together to form one long articular groove ; and the same is the case in all 

 the other sternal ribs. It joins the fourth vertebral rib, and belongs to the twenty- 

 second vertebra. 



The second sternal rib is also longer, more slender, and more curved than in either 

 Struthio or Rhea. 



The same greater elongation and slenderness may be also predicated of the third and 

 fourth sternal ribs. The fourth rib does not always attain the sternum, but may (as in 

 No. 1358) be applied to the postaxial surface of the thii-d rib, ending distaUy in a point. 



THE STEENUM. 



STERNUM OF EMIT (| natural size). 

 Fig. 19. Fig. 20. 



c 



mx 



Fig. 19. Ventral view. 



Fig. 20. Lateral view. 



The sternum much resembles that of Rhea. The coracoid grooves, however, are 

 approximated and very differently conditioned. Their dorsal margins extend so far 

 preaxiad of their ventral margins that their dorsal boundary thus forms a large part of 

 the sternum on each side. The two ventral margins together produce a prominence on 

 the preaxial part of the sternum ; and at the preaxial end of this prominence is a very 

 slight and irregularly shaped notch. There are no lateral xiphoid processes or median 

 postaxial notch. There is an elevated, but not flattened, tract of bone at about the 

 middle of the ventral surface. There are on each side four continuous articular surfaces, 

 with a deep excavation behind and in front of each. The costal angles (fig. 12, ca) are 



VOL. X. — PART I. No. 4. — March, 1877. e 



