CH. Ill] STRUTHIOUS BIRDS. 167 



remains which are in various degrees fragmentary, the 

 actual number of the genera and species is doubtful ; but 

 it seems now to be well established that there were in the 

 more southern regions of the American continent at least 

 three genera of gigantic flightless birds comprising seven 

 or eight species. To these genera the names of Brontornis, 

 Phororhacus and Opisthodactylus have been applied. Some 

 of these birds were actually the largest known forms of 

 Ratites. It appears from certain roughnesses on the 

 bones of the skull that some species bore upon the head 

 a casque like that of the Cassowaries ; though in some 

 respects, thinks Mr Lydekker, the resemblances are with 

 the living and South American Psophia and Cariama 1 . 

 They approximate however to the Dinornithidse in a 

 number of characters which together are of some im- 

 portance ; thus there is with them as in the Dinornithidse 

 a bony bridge over the extensor groove of the tibia, and 

 the general proportions of the tibia and tarso-metatarsus 

 are like those of the same bones in the Dinornithidae. 

 But the significance of the facts from the point of view 

 of Zoogeography is somewhat blurred if we rightly refer 

 to the Ratites, or Platycoracoidese, as Fiirbringer calls 

 them, the European genera Gastornis and Dasornis and 

 the American Diatryma. Fiirbringer however queries 

 the inclusion of the two last in the group, and does not 

 allow Gastornis there at all. Dasornis is only known by 

 an imperfect cranium, and Diatryma by an incomplete 

 tarso-metatarsus, so that this evidence is not at present 



1 See a paper. by Lydekker in Ibis for 1893. - '• ' : 



