100 ox THE CLASSIFinATION OF BiriDS. 
the two or three outermost feathers 
slightly graduated; that is, j)rogressively 
shorter than those more in the raidtUe : 
sometimes the external feather alone is 
abbreviated, as in the robin ; but in the 
stone-chat {Snxicolu ruhicola), the four 
outermost feathers (Jig. 49.) are progres- 
sively shortened. The tails, however, of 
both these birds present a union of two 
forms, for they are rounded, and at the 
same time exhibit the divaricated struc- 
ture, hereafter noticed. 
( 91 .) 3 . K fau-Khwped tail, as its name implies, is so 
much rounded that the two middle feathers are alone 
equal in length, all the others gradually, but gently dlmi.. 
nishing. A fan -shaped tail is always longer than usual, 
and the feathers, besides being broad, have this peculi- 
arity, that the two webs are more equal in breadth than 
in simply rounded tails. This will be evident on com- 
paring one of the featliers of the robin with another of 
the fan-tailed flycatcher of New Holland : in the first the 
shaft appears close to the edge, whereas in the other, 
it is nearly central. This ilistinction, hitherto neg- 
lected, is important, because it enables us to detect a 
habit of the bird, from its mere skin, whicb, otherwise 
could only be known by seeing tbe subject alive, and 
even then, under particular circumstances. This struc- 
ture, however rare among the perchers, is seen in the 
highest development in the peacocks and the turkeys, 
where the tail is of the most gorgeous and splendid 
beauty. It may be considered a law of nature, that all 
fan-tailed birds are representations of the Rasorial type, 
since every one whose affinites have been investigated 
have proved to be so. 4. Gradiinted tails not only ex- 
hibit a greater degree of circularity than those which 
are simply rounded, but they possess this peculiarity, 
that the external feathers, instead of being very slightly 
shorter than those of the middle, are abruptly abbre- 
viated, so that the outermost is often not one third 
