Plate VI., Fig. 1, is a Proximal Barbule cut from a Barb of a Golden Eagle 

 Primary, magnified 90 times. On the upper side the dark line represents a curved 

 edge which provides a ridge for the hamuli to catch on. This will be more 

 cleariy followed by reference to Fig. 2. On the lower side are seen a few teeth. 

 The proximal barbules at the base of the barb terminate in a long filament, but 

 towards the tip of the barb this filament practically disappears. 



Plate VI., Fig. 2, is a transverse section of three Proximal Barbules cut from 

 a Barb of the same Genus Primary, magnified 520 times. In this figure the turn 

 over of the upper edge is plainly seen. 



Plate VI., Fig. 3, shows an oblique section of a Proximal Barbule cut from 

 a Barb of a Golden Eagle Primary, magnified 260 times. Here the continuous 

 nature of the curved edge is more clearly shown as well as the rough texture of 

 the suface of the barbule. 



Plate VI., Fig. 4, is a transverse section of a Barb of a Golden Eagle 

 Primary, magnified 105 times. The distal barbules project on the right and the 

 proximal barbules on the left. It will be noticed that the barbules spring from a 

 different level, the distal barbules being uppermost. The barb extends some 

 way below the level of the barbules. 



Plate VI., Fig. 5, is a transverse sectiori of two Barbs of a Golden Eagle 

 Primary, magnified 150 times. The two barbs in this instance appear in their 

 original positions in order to show the interlocking between the distal and 

 proximal barbules. The barb rises from the lower side of the photograph. On 

 the left there is a notch, out of which springs the proximal barbule. As these 

 barbules are set on the barbs at a very oblique angle, a transverse cut not only 

 severs one barbule but also several more barbules which cross the plane of the 

 cut ; hence the appearance of so many. Following the barb upwards we arrive 

 at a second notch, from which springs the distal barbule. This may be more 

 cleariy appreciated by reference to Fig. 4. The distal barbules overhang the 

 proximal barbules, and the hooks may be seen gripping the curved edges of the 

 proximal barbules. 



9 — 



