THE CLASSIFICATION OF BIRDS 33 



habits. The front digits are ' connected together by a web. In 

 one genus (Pelccanoides) the hallux is absent ; in the Diomedeidce 

 the rudimentary hallux is concealed under the skin, but in all the 

 other Tubinares it is visible though reduced to one phalanx. 



The Tubinares may be divided into three families. The 

 Pujinidcs differ from the other two families in having basiptery- 

 goid processes ; the Diomedeidce -differ from the other two families 

 in having the nasal tubes separated from each other, leaving the 

 Procellariidce as the typical family of the Order. 



9. PYGOPODES. 10. FULICARLE. 



These suborders contain only six families, but they all have 

 very wide geographical ranges, and appear to have become differ- 

 entiated from each other by many and strongly marked characters. 



The Colymbidcc and the Podicipidce differ from the other four 

 families in having the cnemial process of the tibia produced 

 forwards to a remarkable degree, and in having the posterior 

 processes of the ilium approximated to such an extent that the 

 sacrum is almost entirely concealed. 



Of the six families the Colynibidce alone consists of birds with 

 completely webbed feet, but the Podicipidce, the Heliornithidce, 

 and some of the liallidce have lateral lobes on the digits. 



The Otididce and the Heliornithidce agree with the Colynibidcc 

 and Podicipidce, and differ from the CEdicnemidce and Eallidce, in 

 having no lateral bare tracts on the neck. 



The CEdicnemidce are peculiar in having opisthocoelous dorsal 

 vertebrae, and the Otididce in having no oil-gland. The Heliorni- 

 thidce are altrices like the Tubinares, but all the other birds in the 

 Order are prascoces. They have also an important interclavicular 

 process which is attached to the keel of the sternum. The 

 Colymb idee and Podicipidce have the external process, but it is not 

 attached to the keel of the sternum. In the other families the 

 interclavicular process is very small and seldom attached to the 

 keel of the sternum. 



The hallux is absent in the Otididce and in the CEdicnemidce. 



Whether the characters in which the Colymbiclce and Podici- 

 pidce agree with each other and differ from the others may or may 

 not be regarded as of sufficient importance to warrant the com- 

 bination of these two families into a Suborder under the name of 

 Pygopodes, leaving the other four associated together under the 



c 



