CLASSinCATIOX, AND PHYLOGENT OF THE DINOENITHID^. 



425 



than any other genus to Dromceus and Casuarius^. On the other hand, tlie relative 

 size of the orbit is greatest in Anomalopterya;, and the presphenoid fossa or vestige of 

 the interorbital septum is most marked in that genus and in Dinornis : I am disposed, 

 therefore, to derive Mesopterijx and Anomalopterijx from a common ancestor. 



Pachijornis appears undoubtedly to spring from the Mcsopteri/x-stock : these two 

 genera are more nearly allied than any other two, Pachi/ornis being the more differen- 

 tiated in virtue of its greater bulk, broader skull, larger temporal fossae, more widely 

 separated optic foramina, and stronger beak. 



Emeus is derived by Hntton from Mesopteryx, a view which I am strongly inclined 

 to adopt. The cranium of Emeus undoubtedly comes nearest to that of Mesopteryx, 



Dinornis 



Fig. 1. — -rhylogenctic diagram sliowing the mutual relations of the Eatitas. 



the differences between the two skulls depending mainly on the stronger and coarser 

 character of the whole skull, the broader beak, and the scronger mandible of Emeus. I 

 think, therefore, that the latter genus should be considered as springing from the 

 Mesopteryx-stock — not, of course, from Mesopteryx itself, but from an older member of 

 the line of descent which culminated in that genus. 



Dinornis agrees with but goes beyond Pachyornis in its widely^ separated ojitic 



' The striking resemblance of the dried head of Mesopteryx atsuarina {Didomis didinus, Owen) to that of 

 an Emu is noticed by Owen (23). 



