48 A HISTORY OF BIRDS 



rise to these two great branches we cannot, from lack of material, 

 say as yet. That it was an offshoot from the Palseognathine 

 stock is certain, and Dr. Mitchell contends that it is represented 

 to-day by the remarkable aberrant Goose-like birds, Palamedea 

 and Chauna, more commonly known as the "Screamers," 

 natives of South America. 



The descendants of this hypothetical Palamedia-like ancestor 

 would seem to have given rise to a stock of great potentiality, 

 which under the stress of the struggle for existence became 

 more and more differentiated, more and more specialised as the 

 necessity for adaptation to environment became more acute. 

 These descendants, in short, gave rise to what we know to-day 

 as the Neognathine birds, which, as we have already remarked, 

 are divisible into two great groups. 



Let us pass, in brief review, the essential features of the 

 differentiation of the Colymbo-pelargomorphine group. 



Of these, the oldest, the first to become differentiated from 

 this generalised stock, appear to have been the Penguins, 

 Grebes and Divers, including the extinct, giant, toothed Diver 

 of the cretaceous epoch (p. 37), and the Petrels on the one 

 hand ; and the Anserine birds. Storks, and Accipitrine birds 

 on the other. While these were in the making, yet a third 

 group was developing which gave rise to types which are repre- 

 sented to-day by the Steganopodes — Pelicans, Gannets, Cormo- 

 rants and Darters, Frigate and Tropic-birds. Dr. Mitchell 

 Contends that it was this same Steganopodous stock which gave 

 rise to the Penguins, the Petrels, the Stork tribe and Accipitres, 

 but this is a matter for debate. 



Of the Penguins and Petrels we need say little here, the 

 salient points in their evolution being discussed elsewhere in these 

 pages. But of the Stork tribe it is necessary to say that this 

 includes, besides the familiar Storks and Herons — commonly 

 confounded with the Cranes — -several less familiar and aber- 

 rant types ; the Flamingoes, Hammer-head {Scopus), Open-bill 

 {Anastonus), Spoon-bills {Platalea), Ibises and Tantalus Storks, 

 being among the more or less isolated ciconiine or Stork-like 

 forms, and the Whale-headed Stork {Balcenicepo) and Boat-bill 

 {Cancromd) among the Ardeine or Heron-like forms. 



To return for a moment to the Steganopodous birds, it 

 should be mentioned that it is to this group, in all probability. 



