SUBFAMILIES AND GENERA 5 
of convenience rather than of anatomical necessity, are fairly easily 
divisible by simple characteristics in outward form. 
Key to the Genera. 
A. A deep notch in inner web of third primary ; tail neither 
greatly graduated nor with central tail-feathers 
prolonged : 
a. Horny part of bill does not extend along culmen to 
edge of feathers of fore-head : 
a’ First three primaries acuminate, legs yellow Crocopus. 
b’ First three primaries not acuminate ; legs red : 
a” Horny part of bill less than two-thirds 
of culmen Osmotreron. 
b” Horny part of bill n more than two- thirds 
of culmen af Butreron. 
6. Horny part of bill extends ae ‘he ieee to the 
feathers of fore-head . Treron. 
B. Inner web of third primary with no notch; tail much 
graduated and lengthened ag Bey ...  Sphenocercus. 
