166 



Trowbridge — Interlocking of Emarginate 



be bent upwards by the air pressure. They are then not only 

 extended in a horizontal plane but also separated to some 

 extent in a vertical plane. Under these circumstances while 

 the primaries would appear widely apart, they might readily 



Fig. 17. Primaries not interlocked, viewed from in front of the wing. 



18 



Fig. IS. Primaries interlocked, viewed from in front of the wing. 



19 



Fig. 19. The bowed effect of the wings is seen in many species in [swift 

 coasting flight. The twist of the wing is shown as given by Pettigrew.* 



be held in an extended position, or in other words interlocked, 

 by the emarginations, thus forming a firm stepped aeroplane at 

 the end of the wing. 



* Pettigrew, Animal Locomotion, p. 186 and 198. 



