SKELETON OF THE WILD DUCK. THE FEATHERS. 303 



bears two holes : one, the inferior umbilicus, is at its 

 proximal end, and into it enters a vascular outgrowth from the 

 dermis; the other, the superior umbilicus, lies on the 

 ventral surface at the junction of the calamus and scapus. 



The barbs are a series of narrow elastic plates, attached 

 by their bases to the rachis, and with their edges looking 

 upwards and downwards. The barbs are connected together 

 by a number of smaller processes, the barbules, which inter- 

 lock with one another by means of booklets, and bear the 

 same relation to the barbs that the barbs do to the rachis. 

 The barbs and barbules, together with the rachis, constitute 

 the vexillum or vane of the feather. Any feather having 

 the above type of structure is called a penna or a contour 

 feather, from the fact that it helps to produce the contour of 

 the body. 



VARIETIES OF FEATHERS. 



1. Pennae. There are two kinds of pennae or contour 

 feathers. 



(a) The quills. These form the large feathers of the 

 wing and tail. They are divided into two groups, the 

 remiges, or wing quills, and the rectrices, or tail quills. 



The remiges l include three sets of feathers, the primaries 

 or metacarpo-digitals, which are attached to the bones of 

 the manus, the secondaries or cubitals, which are attached 

 to the ulna, and the humerals, which are attached to the 

 humerus. 



The primaries differ from all the other quill feathers 

 in having the posterior half of the vane much wider than the 

 anterior half. They are ten in number, and of these six, 

 the metacarpal quills (fig. 57, 14), are attached to the second 

 and third metacarpals, one, the ad-digital (fig. 57, 15), to the 

 phalanx of the third digit, two, the mid-digitals (fig. 57, 16). 

 to the first phalanx of the second digit, and two, the pre-digitals 



1 See E. S. Wray, P. Z. S., 1887, p. 343. 



