1466 



BIRDS 



apparent that the so-called tail of a bird does not correspond with the tail of a Mam- 

 mal. In the earliest-known bird the tail was, however, long, and composed of a 



number of vertebras, 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 (/>, /') 

 is directed backward parallel with 

 the element termed the ischium; 

 the three elements being united as 

 in Mammals but differing from 

 them, with two exceptions, in that 

 neither the ischium nor the pubis 

 unites with its fellow of the op- 

 posite side in the middle line. 

 LEFT SIDE OF SHOULDER BONES AND BREASTBONE Moreover, the cup in the pelvis for 



OF A FLIGHTLESS BIRD. . . 



the head of the thigh bone is always 



s. blade bone or scapula; c. metacoracoid; h. arm bone or ___ _i ii-o V>oe<=> T'Vio firm iitii/vn 

 ,, f .*. OTJcH il L LUC L)doCr. -L He illlll UIllOll 



humerus ; f. furcula ; st. breastbone or sternum. After Marsh. 



of the haunch bones with such a 



large portion of the backbone is necessary to afford a solid basis of support for the 

 rest of the skeleton in flight. 



Equally essential is a solid union between the bones of the shoulder and the 

 breastbone. Accordingly, we find that, as in the Egg-laying Mammals the blade 

 bone or scapula (s) is connected with the breastbone (.?/), by a metacoracoid (f); 

 the scapula and metacoracoid thus jointly forming the cup for the articulation 

 of the head of the arm bone or humerus (h}. Although in 

 flightless birds the metacoracoid is short and broad, in other 

 species it is more or less elongated, and in either case its 

 lower expanded end is received in a groove on the summit 

 of the breastbone. Usually the collar bones, or clavicles, are 

 well developed, and united to form a V or U-shaped bone, 

 now known as the "merrythought," or furcula (/); this 

 furcula generally articulating with a process on the metacora- 

 coid (a), and also with the anterior end of the breastbone. 

 The breastbone in flying birds is provided with a strong 

 keel up the middle of its inferior surface, as shown in the 

 figure of the skeleton of a parrot on p. 1464, in order to afford 

 support for the powerful muscles moving the wing; but in 

 flightless birds, as in the figure on this page, it is smooth FRONT SURFACE OF 

 and rounded. To the sides of the upper part of the breast- THE LEFT ME J ACOR ; 



ACOID OF A FLYING 



bone are attached the lower segments of the ribs; the ribs BIRD. 



themselves being few in number, and distinguished from a . process for articulation 



those of Mammals by the presence of oblique (uncinate) f furcula; *, c, d. surface 



... ,. .,1 i i i i for junction with breast- 



processes projecting from their hinder borders. bone. 



