HIGH SCHOOL ZOOLOGY. 



137 



tlie spficies l)elong, hut which exhibit far less important tliffer- 

 oncos between each other than do the members of the lower 

 orders. 



1 7. The following arrangement of the orders of Carinatfe is tliat gener- 

 ally employed ; although there may be doubt as to the affinities of some 

 of the groups, there is none that the swimming birds occu^jy the lowest 

 place and the song birds the highest. Of the former the Pygopodes, or' 

 Divers, are marked by the far back position of the legs required by an 

 erect or semi-erect at- 

 titude, by the short- 

 ness or rudimentary 

 characterofthewings, 

 by the complete or 

 incomplete webbing 

 of the three toes, and 

 by their powers of 

 swimming and div- 

 ing. The most re- 

 markable genus is the 

 Fengnin{Aptenodutf. 

 of Southern Seas, 

 (Fig. 88) in which 

 tlie power of flight 

 has been lost, and the 

 wings are converted 

 into flippers covered 

 with scale-like feath- 

 ers. Another inter- 

 esting form, in which 

 the wings, thouj 

 feathered, were ex- 

 tremely short and in- 

 capable of flight, is the 

 great Auk (Plautus 

 hnpennis (Fig. 99), 

 which was common ia 

 the Arctic Seas at the beginning of this century, but is now thought to be 

 quite extinct. Allied to it are the Vw^m^iFrahrcida) with their singularly 

 shaped and brilliantly coloured bills, and the Sea-pigeons (Crpphiis grylle) 



10 



Fig. 98.— Pen^T'iin (Aptenodytes) 

 (after lirehui.) 



