8 Mr. Burton on the Natural History and Anatomy 



which the muscles are attached, serving to lighten these parts 

 still more. The acetabulum is also a large foramen, with the 

 circumference a little raised and thickened ; and the head of the 

 os femoris is so irregular, that its motion in the acetabulum must 

 be very limited and imperfect ; forming an additional proof how 

 useless this extremity is to the bird. 



The structure of the bones of the tail forms one of the most 

 remarkable parts of the skeleton. They are adapted to give 

 support to the great mass of tail-feathers, and form a surface of 

 attachment for the numerous muscles necessary to the various 

 and extensive motions of the tail. They are seven in number, 

 six of which are vertebras, totally distinct from, and having a 

 great degree of motion in every direction, on each other. A large 

 and strong spinous process arises from every bone nearly per- 

 pendicularly, and two long and thick lateral processes, varying 

 in length from half to three quarters of an inch, and connected 

 to each other by lateral ligaments. Every bone, between the 

 spinous process and its body, is perforated for lodging the con- 

 tinuation of the spinal marrow. The upper vertebra is the 

 smallest, the size progressively increasing to the last, which is the 

 largest of the six. The lateral processes of the upper vertebra 

 have a bony union with the pelvis, as well as the inner surface 

 of the body. Each vertebra has small obtuse articulating pro- 

 cesses, the inferior being most conspicuous. The two last ver- 

 tebrae are furnished with additional processes, no appearance of 

 which is to be found in the others : these have a common ori- 

 gin from the inner surface of the body of the bone, immediately 

 become forked, and are turned obliquely towards the vertebra 

 above, over which thdy lap, serving to give additional attach- 

 ment to muscles. The structure of the seventh bone is altogether 

 different from any of the preceding : in shape it has some ana- 

 logy to the vomer of the human cranium, but is less in size, its 



longest 



