AXIAL SKELETON OF THE STRUTHIONID. 25 
The frst sternal rib is rather shorter than the second vertebral rib, and is rather 
more slender and curved than in Struthio or Rhea. 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 third rib, ending distally in a point. 
THE STERNUM. 
STERNUM OF EMU (Z natural size). 
Fig. 19. Fig. 20. 

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. ‘heir 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.—Warch, 1877. E 
