CH. I] THE GALLINACEOUS BIRDS. 27 



families 1 : Grouse, Turkeys, Guinea-fowls, Pheasants, 

 Megapodes, Curassows and the aberrant Hoatzin (Opis- 

 thocomus). They are thus distributed : 



1. Tetraonidae (Grouse). Palsearctic and Nearctic. 



2. Phasianidae (Pheasants). Oriental. 



3. Numididae (Guinea-fowls). Ethiopian. 



4. Meleagrida? (Turkeys). Southern Nearctic. 



5. Cracidae (Curassows). Neotropical. 



6. Megapodidae (Mound-builders). Australian. 



7. Opisthocomidae (Hoatzin). Neotropical 2 . 



They are not, however, in every case absolutely confined 

 to these regions as defined by Mr Sclater. Thus among 

 the Megapodes one species gets into the Indian region, 

 and the Phasianidae stray into the Palaearctic. The 

 Tetraonidae are really almost cosmopolitan, though mainly 

 massed in the two northern regions of the earth's surface. 

 The Curassows extend into the southern parts of the 

 Nearctic, occurring as they do in Mexico and in California. 

 Such briefly are the facts of the distribution of this group 

 of birds ; it now remains to enquire into the mutual 

 relationships of the several families or subfamilies. Mr 

 Huxley unites the Megapodes with the Cracidae into 

 a group Peristeropodes, and separates them from all the 

 rest which constitute his Alectoropodes. The former 

 division has a sternum with less deeply marked notches, 

 the vomer is well-developed, and the hallux is attached to 

 the foot on a level with the other toes. These characters 

 look as if they were more primitive than the deeply 



1 P.Z.S. 1868. 



- These terms are explained later ; see Chap. II. 



