122 



GENERAL OBNITHOLOGY. 



have received particular names. A rectrix broad to the very tip, and there cut squarely off, is 

 said to be truncate ; one such cut obliquely off is incised, especially when, as often happens, the 

 outline of the cut-off is concave. A linear rectrix is very narrow, with parallel sides; a lanceo- 

 late one is broader at the base, thence tapering regularly and gradually to the tip. A notably 

 pointed rectrix is said to be acute; when the pointing is produced by abrupt centraction near the 

 tip, as in most woodpeckers, the feather is acuminate. A very long and slender, more or less 

 linear feather is called filamentous, as the lateral pair of a barn swallow or most sea swallows. 

 The vanes sometimes enlarge abruptly at the end, forming a spoon-shaped or sjmtulate feather; 



or such a spoon may 

 result from narrowing 

 of the vanes near the 

 end, or their entire ab- 

 sence, as in the "rack- 

 et " of a saw-bill (3Io- 

 motus). The vanes are 

 sometimes wavy as if 

 crimped; our Plotus is 

 a fine example of this. 

 Sometimes the vanes 

 are entirely loosened, 

 the barbs being remote 

 from each other, as in 

 the exotic genus Stipi- 

 turus, and some parts 

 of the wonderful caudal 

 appendage of the male 

 lyre-bird (Menura su- 

 perba). When the rha- 

 (his projects beyond the 

 \anes, the feather is 

 ^pinose, or better, mu- 

 ironate (Lat. muero, a 

 pricker), as excellently 

 -<hown in the chimney- 

 ^ivift, ChtEtura (fig. 

 3 75). A pair of feathers 

 abruptly extending far 

 beyond the others are 

 Tail-featliers also differ 



■^f3^:-^ 



to >.liow the mil jue 



Fig 32 — Ihe I\relirl ot Au^iiilii ytiiuia ii 

 lyrate shape of the tail (From Amer lyat ) 



called long-exserted, after the analogous use of the term in botany, 

 much in their consistency, from the softest and weakest, not well distinguished from coverts, 

 to such stiff and rugged props as the woodpeckers possess. They are downy and very rudi- 

 mentary in a few birds, notably all the grebes, Podicipedidce, which are commonly said to 

 have no tail. The tinamous of South America (Dromceognathce) are also very closely 

 docked. The 



Typical Number of Rectrices is twelve. This holds in the great majority of birds. It 

 is so uniform throughout the great group Oscines, that the rare exceptions seem perfectly 

 anomalous (ten in Edoliidce or Dicr\irid(p). In the other group of Passeres (Clamatores) it is 

 usually twelve, sometimes ten. Ten is the rule among Picarice, though mauy have twelve, a 

 very few only eight, as in the genus Crotophaga. The whole of the woodpeckers (PicidcB) 



