1885.] 



DR. H. GADOW ON THE SPECIES OF RHEA. 



311 



americana possessing this foramen reduce its presence or absence to 

 an unimportant individual variation. 



Regarding the vertebral column, the three species exhibit some 



Fig. 4. 



Skull of Bh. americana, ? natural size. Side view. 



Fiff. 5. 



Skull of Bh. macrorhyncha, I natural size. Side view. 



Fig. 6. 



Skull of Bh. darwini, | natural size. Side view. 



highly interesting differences, which would be of great impor- 

 tance 'if we could be certain that they are not due to individual 

 variation. 



21* 



