PHYLOGENT OF THE PAL^EOGNATH/E AND NEOGNATH^E. 275 



Key to the Species. 



Struthio. 



a. Middle region of anterior border straight or slightly arched; length of 



coracoid groove greater than distance between articulations of sternal 

 ribs 1-5. 

 a'. Posterior lateral processes long and spatulate, with an extensively ossified 



metasternal region between the posterior lateral processes <S. molybdophanes. 



b' . Posterior lateral processes moderately long; ossified metasternal region 



between posterior lateral processes small S. camelus. 



b. Middle region of anterior border of sternum sinuous ; posterior lateral pro- 



cesses not spatulate ; no projecting metasternal region between the 



posterior lateral processes ; length of coracoid groove less than the 



distance between the articulations of sternal ribs 1-5. 

 c'. Width between the free end of the anterior lateral processes much greater 



than the width across their bases S. meridionalis. 



d'. Width across free end of posterior lateral processes about equal to the 



width across their bases S. australis. 



Rhea. 



a. Anterior border of sternum between the coracoid grooves slightly excavated ; 



width between right and left coracoid grooves greater than length of 



articular surface for coracoid ; articular surfaces for sternal ribs 3 . . . R. americana. 



b. Outer border of sternum between the coracoid grooves deeply excavated ; 



width between right and left coracoid grooves equal to or less than length of 



articular surface for coracoid ; articular surfaces for sternal ribs 4 . . . R. macrorhyncha. 



DROMjEUS. 



a. Length 6£ in. Coracoid grooves distinct and the sternal protuberance but 



slightly developed D. nova-hollandia. 



b. Length not exceeding 3 7 g in. ; coracoid grooves obsolete ; the ventral lip of 



rio-ht side only represented ; sternal protuberance conspicuous D. ater. 



Casuarius. 



A. With a pair of low, median, keel-like ridges lying immediately behind a line 



drawn across the sternum immediately behind the coracoid grooves, without 



median pneumatic cavity between the coracoid grooves C. unappendiculat 



B. Without paired median ridges ; with large pneumatic cavity between the 



coracoid grooves. 

 a. Coracoid grooves deep, the lower lip strongly marked when seen from 

 above; pneumatic cavity very large, extending backwards into a low 

 swollen protuberance lying in the middle line of the sternum between 

 the coracoid grooves. 



us. 



