774 Mr. W. P. Pycraft on the 



hand with the ^pyornithidae o£ Madagascar, and on the 

 other with the Dinornithidae of New Zealand. 



This interpretation is borne out by the evidence furnished 

 by the distal end of the tibio-tarsus of an indubitably 

 Struthious bird — Eremopezus eoccenus — from the upper 

 Eocene of Birket-el-Querun, Fay urn. This fragment, 

 remarks Dr. C. W. Andrews, who discovered it, bears a close 

 likeness to the distal end of the tibio-tarsus of the 

 Dromseidfe and the Rheidse, rather than to that of the 

 ^pyornithidae or Struthionidse. Thus the Ethiopian region 

 has produced at least three Struthious types, members of 

 which seem to have passed westwards on the one hand into 

 South America, giving rise to the Rheidse and Tinaraidpe, 

 and eastwards on the other, giving rise to the Dromaeidse 

 and Dinornithidae. The discovery of phalangeal bones of a 

 Struthious l)ird apparently nearly allied to the Emus in the 

 Pliocene of the Siwaliks, lends further support to this inter- 

 pretation. It is to be hoped that remains will yet be found 

 of the pelvis of Eremopezus and of tlie Indian Hypselornis, 

 for it is to be noted that the pelvic girdle of ^pyornis, 

 Dinornis, and the Tinamous is of the typical broad type ; 

 while that of Struthio, Rhea, and Dromaus is laterally com- 

 pressed to a remarkable degree. This point, however, raises 

 questions which have but an indirect bearing on the present 

 problem. 



Summary. 



A very brief survey of the avifauna of Mexico and Central 

 America will show that it is composed in part of Nearctic, 

 and in part of Neotropical species, the latter predominating, 

 while some are endemic. 



Examined in more detail, it will be found that the repre- 

 sentatives of the tropical (South-American) species are in 

 part the descendants of the autochthonous South-American 

 fauna, and in part of South-American species derived from 

 the Old World and apparently from Africa. These migra- 

 tions, it is important to note, have been performed in each 

 case, not by sudden and swift aerial journeys, but by means 

 of a slow increase of range over a continuous land-surface ; 



