Key of the Families. 



(In this key, which is intended only for the easy recognition of 

 the position of any particular unknown bird, only the external and 

 easily recognisable characters are used. For the full anatomical 

 details recourse must be had to the descriptions of each family.) 



A. Feet with three toes forwardly, the 



first or hallux backwardly directed. 



a. The third and fourth toes united along 



their basal joint at least (syn- 

 dactylous). 

 l . With ten tail-feathers. 



a?. Under wing-coverts normal; 

 tarsus scutellated posteriorly. 



a?. Head crested Upupidce, p. 9. 



6 3 . Head without crest Irrisoridce, p. 13. 



b*. Under wing-coverts not covering 

 the quills below ; posterior 

 aspect of tarsus covered with 



small scales Bucerotidce, p. 100. 



&'. With twelve tail-feathers. 

 a 2 . Bill long, slender and curved ; 



ten primaries Meropidce, p. 55. 



b 2 . Bill long, but stout and straight ; 



eleven primaries Alcedinidce, p. 71. 



b. The third and fourth toes only united 



by a slight web not extending as 

 far as the first joint ; claw of the 

 middle toe pectinated Caprimulgidce, p. 31. 



c. The third and fourth tpes quite free 



from one another* fourth toe 



reversible at will. 



a^. With twelve tail-feathers Coraciidce, p. 45. 



b\ With ten tail-feathers Musophagidce, p. 212. 



B. Feet with all four toes forwardly di- 



rected (pamprodactylous). 



a. Bill very small with wide gape ; 



secondaries very short and less 



than nine in number Cypselidce, p. 19. 



b. Bill short and finch-like ; secondaries 



normal, more than nine in number Collides, p. 93. 



C. Feet with third and fourth toes for- 



wardly, first and second backwardly 



directed (heterodactylous) Trogonida, p. 120. 



D. Feet with second and third forwardly, 



first and fourth backwardly directed 

 (zygodactylous). 



