34 



ZOOLOGY. 



the " ploughshare bone," and is nearly perpendicular to 

 the vertebral column. It supports the large quill feathers 

 of the tail. In an extinct bird, the archseopteryx (Gr. 

 archaios, ancient ; pteryx, a wing), whose remains are 

 found in the oolitic rocks, there was no ploughshare bone, 

 and the tail consisted of twenty distinct vertebrae, each of 

 which bore a pair of quill feathers. 



The sternum is very large, and in flying birds is pro- 

 vided with a ridge or "keel." To the sternum, the muscles 

 which move the wings are attached. The keel is absent 

 in the Cursores, an order which includes the ostrich, 

 emeu, cassowary, &c. The number of ribs varies from 

 seven to eleven pairs. 



FIG. 9. STERNUM, FURCULUM, SCAPULAE, AND CORACOID BONES OP 

 A SPARROW. 



The scapula, clavicle, and coracoid bone form what is 

 called the " pectoral arch." The clavicles are united in 

 front, forming a Y-shaped bone, which is termed the 

 furculum (Lat. furca, a fork) or " merrythought." The 

 coracoid (Gr. Jcorax, a crow) bone corresponds to the 

 " coracoid process" in man, but in birds is a distinct 

 bone. It is united at one end to the clavicle and scapula, 

 at the other to the sternum. 



Of the fore-limb or wing, the upper bone is the 



