SEC. in EXTERIOR PARTS OF BIRDS 169 



III. THE TAIL. 



Its Bony Basis. — Time was when birds flew about with long, 

 Hzard-hke, bony, and fleshy tails, having the feathers inserted in a 

 row on either side like the hairs of a squirrel's. But we have 

 changed all that distichous arrangement since when the Archceopteryx 

 was steered with such a rudder through the scenes of its Jurassic 

 life. Now the true separate coccygeal bones are few, generally 

 about nine in number, and so short and stunted that they do not 

 project beyond the general plumage — in fact, scarcely beyond the 

 border of the pelvis. Anteriorly, within the bony basin of the 

 pelvis, there are several vertebrae, which, fusing together and with 

 the true sacrum, are termed urosacral or false tail-bones. To these 

 succeed the true caudal vertebrae, movable upon each other and 

 upon the urosacrum. The last one of these, abruptly larger than 

 the rest, and of peculiar shape, bears all the large tail-feathers, 

 which radiate from it like the blades of a fan. The true caudal 

 vertebrae collectively form the coccyx (Gr. kokkv^, koJchix, a cuckoo ; 

 from fancied resemblance of the human tail-bones to a cuckoo's 

 bill; Fig. 56, civ); the enlarged terminal one is the vomer (Lat. 

 vomer, a ploughshare, from its shape ; not to be confused with a 

 bone of the skull of same name) or pygostyle (Gr. Trvyri, puge, rump, 

 and (TTuAos, stulos, a stake, pale ; Fig. 5Q,pt/). The pygostyle, how- 

 ever, is a compound bone, consisting of several stunted coccygeal 

 vertebrae fused in one. The bones are moved by appropriate 

 muscles, and upon the surface is seated the elaeodochon (p. 129). 

 The whole bony and muscular afiair is familiar to every one as the 

 "pope's nose" of the Christmas turkey; it is a bird's real tail, of 

 ■which the feathers are merely appendages. In descriptive ornitho- 

 logy, however, the anatomical parts are ignored, the word " tail " 

 having reference solely to the feathers. These, like those of the 

 wings, are of two sorts : the coverts or iectrices, and the rudders or 

 redrices (Lat. rectrix, pi. rectrices, a ruler, guider ; because they seem 

 to steer the bird's flight) ; corresponding exactly to the coverts and 

 remiges of the wings. The 



Tail-Coverts are the numerous comparatively small and weak 

 feathers which overlie and underlie the rectrices, covering their 

 bases and extending a variable distance toward their ends, con- 

 tributing to the firmness and symmetry of the tail. They pass 

 smoothly out from the body, by gradual lengthening, there being 

 seldom, if ever, any obvious outward distinction between them and 

 feathers of the rump and belly ; but they belong to the pteryla 

 caudalis (p. 131). The natural division of the coverts is into an 

 upper and under set (iectrices superiores, tectrices inferiores). The 



