OSTEOLOGIA AVIUM. v 



some of these, however, are not to be absolutely relied upon, namely the characters 

 derivable from the fissures and foramina at the posterior margin. I have many skeletons 

 in which the two sides do not correspond. The order Kaptores seems particularly 

 liable to this variation ; and I have also an Alcedo which has a foramen on one side 

 and a fissure on the opposite one. The form of the keel, and whether it is produced 

 anteriorly or not, forms a valuable character. 



The characters found in the bones of the pelvis are very well marked ; they depend 

 chiefly upon the proportion between the breadth and length, the size and shape of the 

 obturator and ischiadic foramina, the relative position of the ilium and ischium, and 

 whether the former is expanded anteriorly or not. 



The ribs vary much in their form, breadth, and strength, and in the length of the 

 posterior styliform process. 



The bones of the anterior extremity are composed of the scapula, coracoid, furculum, 

 and wing bones ; they vary much : the former is much flattened or rounded, straight 

 or much deflexed ; the coracoids are long or short, strong, weak, or are pierced with an 

 axillary foramen; the furculum is sometimes found much arched forwards, at others 

 nearly straight — sometimes reaching as far as the point of the keel and anchylosed to 

 it, in other birds not reaching it, and in some altogether wanting. 



The wing bones are very remarkable in some of the water birds (Spheniscus), forming 

 a sort of fin, and furnish good characters in the proportionate length of one to the 

 other. 



The bones of the posterior extremity vary very much in their strength, length, and 

 relative proportions one to the other. Very valuable characters are also derivable from 

 the metatarsus : whether the component parts of it, named by Professor Owen the 

 ectometatarsal, mesometatarsal, and entometatarsal, are perfectly anchylosed together, 

 or for what portion of their length they are so ; and also in the position of the trochlea 

 for the articulation of the phalanges forming the feet. In the phalanges themselves 

 no very distinct character is observable, except in the terminal ones, the character of 

 which can be equally well observed externally in their horny covering or claw. 



The vertebral column, although substantially following the same type, is subject to 

 considerable variation, besides that which is derived from the numbers of the vertebrae 

 of the different regions ; and in one instance (Spheniscus) some of them have a ball and 

 socket articulation. 



