Key to the Species, 
A, Larger; wing over 320 mm. 
a\ Wing 325-350 mm. 
h'. Wing 350-370 mm. ; lighter . . 
c'. Wing over 370 mm. ; lightest 
B. Smaller ; wing under 320 mm. 
. . Th, bergii poliocercus, p. 340. 
. . Th. bergii pelecanoides, p. 348, 
. . Th. bergii gwendolence, p 350. 
Th. bengalensis torresii, p. 352. 
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