ORIGIN AND CHARACTERISTICS 33 



the posterior margin of the sternum occur, in 

 others but one. These peculiarities appear to 

 possess little taxonomic value, the configuration 

 of the anterior portion of the sternum being 

 more important in this respect. The next por- 

 tion of a bird's skeleton that we have to 

 consider is the pelvis, composed of a number 

 of fused vertebrae together with three bones 

 on either side, the largest and most dorsal of 

 which is called the Ilium, the ventral or middle 

 one termed the Ischium, and the anterior and 

 most slender of all known as the Os pubis, 

 and all meeting at the acetabulum or cup of 

 the pelvis in which the head of the femur or 

 thigh-bone articulates. These three paired bones 

 coalesce with each other at an early stage of 

 the bird's existence, whilst the notch between 

 the two first named of these bones becomes a 

 foramen in all known birds with the exception 

 of the archaic Ratitae and Crypturi. From the 

 trunk of the skeleton we now pass to a brief 

 notice of the bones of the limbs. We will 

 take those of the wings or anterior limbs first. 

 These consist of the Humerus or upper arm- 

 bone which articulates with the coracoid and 

 scapula, the Ulna and Radius which together 

 compose the forearm, and the Carpus or wrist, 



