LIMBS 



405 



clavicle, the three bones together making the ' merry thought ' 

 or furcula. Where scapula, coracoid, and clavicle join, a small open- 

 ing, the foramen triosseum, is left between them. The sternum is 

 a broad plate, bearing below a conspicuous median keel or carina 

 for the attachment of the great wing muscles, behind two xiphoid 

 processes, at the sides facets for the ribs, and in front surfaces 



mc. 



Fig. 320. — The fore-limb and hind-limb of a bird compared. — From Thomson. 



//., Humerus ; R., radius ; U., ulna ; r., radiale ; u., ulnare ; C, distal carpals united to carpometacarpus; 

 CC, the whole carpal region ; MCI., metacarpal of the thumb ; /., phalanx of the thumb ; ML. II., 

 second metacarpus; //.. second digit; MC.III.. third metacarpus; ///.. third digit; F., femur; 

 T.T., tibiotarsus ; Ft., fibula ; Pt., proximal tarsals united to lower end of tibia ; dt., distal tarsals 

 united to upper end of metatarsus, forming a tarsometatarsus (T.M.T.) ; T., entire tarsal region; 

 MT.L, first metatarsal, free ; I. -IV., toes. 



for the articulation of the coracoid bones. In the wing skeleton 

 (Fig. 320) there is a short, stout humerus, a parallel radius and 

 ulna, rather widely separated except at their ends, where they 

 touch, and two free carpal bones, w^hich are the radiale and ulnare. 

 The bones of the distal row have fused with three metacarpals 

 to form a single carpometacarpus. There are only three digits, 

 the phalanx formula being 12100. 



In the pelvic girdle there is a long ilium, reaching a good way 

 behind as well as in front of the acetabulum, and connected 



