EXTEIINAL ANATOMY. — SCANSOHIAL TAII.. 107 
stances so hard and rigid that it appears more like horn 
than of the ordinary substance. Thus far all scansorial 
tails are constructed alike, hut there are several curious 
modifications in the other details which deserve our at- 
tention, because they serve to characterise different groups. 
The most typical form is seen in the woodpeckers 
{fig. 55. a), all of which possess it, with the exception 
of one type, the genus AHhenuriu-, represented by the 
minute woodpecker of Lin- 
mean authors : in the 
others, not only the shafts 
but the webs are unusu- 
ally stiff, and always show 
the appearance of being 
worn at their extremities 
by their frequent applica- 
tion to the trunks of trees : 
all these feathers are lan- 
ceolate, that is, terminat- 
ing gradually in a point ; 
the webs diminishing- in 
breadth as they approach 
the extremity, but which 
is never naked ; most of 
them, also, have the webs on both sides nearly equal. 
The next modification is seen in the family of Ce)'- 
thiudte or creepers, but more especially in the Brazilian 
gams Di'udrocnluptes ; here we find the external shaft 
very narrow, while the internal is remarkably broad ; 
both, however, terminate before reaching the extrendty 
of the feather ; so that about a quarter of an inch of the 
shaft, at its tip, is entirely naked, and the tip itself 
acutely pointed and inclined downward. 'I’his structure 
will be perfectly understood by the annexed figure (ft), 
while the the abrupt manner in whieh the broad inner 
shaft terminates is bettor seen in the genus Oxjjurus. 
{fig. 5(). n ) Now it is quite clear, that a tail thus 
constructed has equal, if not greater power than that of 
the woodpecker in assisting a bird to climb, inasmuch as 
