GENERAL CHARACTERISTICS. 



293 



As regards the backbone, existing Birds differ from Mammals in that the 

 bodies of the vertebrae, at least in the region of the neck, are articulated to one 

 another by saddle-shaped surfaces, instead of by a cup-and-ball joint or two nearly 

 flat surfaces; and there is no constancy in the number of joints in the neck. 

 A further peculiarity is that a number of the vertebras of the back, together with 

 some of those of the tail, are solidly united with the proper sacrum, while the 

 whole long series of welded vertebras are themselves as firmly attached to the 



ANTERIOR ASPECT OF THE DORSAL VERTEBRA OF A JIOA (Pachl/Omis.) 



ns, upper or neural spine ; n, neural canal ; pz, prezygapophysis ; J. transverse process : v, pedicle of arch ; 

 p, facet for rib ; ac, anterior surface of body or centrum ; hy, lower or luenial spine. — After Owen. 



haunch-bones of the pelvis. In all living Birds the bones of the tail are very few 

 in number, and terminate in a triangular bone (as seen in our figure of the 

 skeleton of a parrot), termed the ploughshare-bone. It is to this region of 

 the body that the tail-feathers of a bird, commonly called the tail, are attached : 

 and it will thus be apparent that the so-called tail of a bird does not correspond 

 with the tail of a mammal. In the earliest known bird the tail was, however, 

 long, and composed of a number of vertebrae, each carrying a pair of feathers. 

 The pelvis of a bird is remarkable for the great elongation of the haunch-bones, 

 and also for the circumstance that the portion known as the pubis {p, p) is 



