Key to the Species. 
A. Smaller : wing under 280 mm. ; culmen under 
55 mm. ; feathering extending on to sides of 
lower mandible H. fuscescens, p. 179. 
B. Larger : wing over 280 mm. ; culmen over 
65 mm. ; no feathering on sides of lower 
mandible . . . . . . . . . . . . H. varius perthi, p. 184. 
X 
