The following portion of this work has been published in the April, 1918. issue of 

 The Ibis," and the plates are reprints of those which appeared in that Journal. 



My attention has been concentrated on the glazed portion of the underside 

 of the Primaries of certain birds. Chandler (University of California Publica- 

 tions, Zoology, xiii. 1916, pp. 243—446), referring to the subject states :— 



" The ventral edges of the rami are produced into horny keels 

 usually with no evident cell structure, known as the ventral ridges. 

 Although in the great majority of birds the ridge forms only a narrow, 

 inconspicuous border for the ramus, in a few birds it is extraordinarily 

 developed as a very thin translucent film, which bends distally and 

 overlaps the following ramus, giving a smooth, glazed appearance to 

 the under surface of the feather which is conspicuous at the most casual 



1 ft 



glance. 



My examination of the ventral ridge indicates that when present in complete 

 form it extends about half the length of the barbs. It is widest at the rhachis 

 end and tapers to a fine point. Prior to perusal of Chandler's work I named this 

 cover of the space between the barbs as the " Tegmen," which for convenience 1 

 continue to use, as there is a considerable difference between a ventral ridge and 

 a fully-developed tegmen. 



The Tegmen is particularly developed in water- and game-birds as well as 

 in the Turkey. The Heron has a dark brown ventral ridge which, though not 

 large enough to form a complete tegmen, is sufficient to create the general appear- 

 ance of tegmenous structure, but instead of a glazed surface it resembles brown 

 velvet when the feather is held at a suitable angle to the light. I find this Heron- 

 like structure is not uncommon, but as it does not come under the head of "a 

 tegmen " the subject has not been specially studied. 



1 find three types of Barbs :— 



1. The flat barb, which may or may not have a ventral ridge and 



gives no indication whatever of a tegmen. 



2. The curved barb, which, having a coloured ventral ridge, gives a 



tegmenous appearance to the underside of a feather. 



3. The flat or curved barb with fully-developed tegmen. 



Type 1 includes the Passeres, Picarise, Columbae, Fulicariae, Alectorides, 

 and Pygopodes. 



Type 2 is represented by the Accipitres, Steganopodes, Herodiones, 

 Pteroclites, and Limicolse. 



Type 3 is found in the Striges, Anseres, Gallinae, and Gavise. 



— 10- 



