ATTAT. SKELETON OF THE STEUTHIONID^E. 



45 



may be three in number ; or they may probably be only two, as appears to be the case 

 in D. elephantopus. 



THE STERNUM. 



The sternum of JDinornis is, as it were, an exaggeration of the sternum of Apteryx. 

 The coracoid-grooves are all but obsolete, so exceedingly faint is the concavity formed 

 by them on the costal angle. The pleurosteon is reduced to a small irregular surface 

 postaxiad of the root of the costal angle, and may bear three articular surfaces, as in D. 

 rheides and D. didiformis, or only two, as in £>. elephantopus. There is no preaxial 

 median process, groove, or fossa ; but one straight rounded surface bounds the sternum 

 preaxially. The costal angles are of moderate size. The lateral xiphoid processes are 

 very prolonged and slender, extraordinarily so in B. rheides. They may be directed 

 postaxiad in an almost parallel direction, as in the last-mentioned species ; or they 

 strongly diverge postaxiad as in B. elephantopus. The median xiphoid process is very 

 large, and, of course, separated from the lateral xiphoids by great notches. It may be 

 very wide at its root, as in B. elephantopus, or rather narrow as in B. rheides. It has 

 always a more or less pointed postaxial termination. 



CHARACTERS COMMON TO STRUTIIIO AND RHEA. 



Axis vertebra with a hypapophysis, with or without well-developed hyperapophyses ; 

 cervical vertebrae greatly elongated ; neural spines of cervical vertebrae small or almost 

 obsolete ; catapophyses commencing about the sixth vertebra ; catapophyses never 

 forming a ring ; diapophysial lamella extending towards posterior zygapophysis, small 



