SKELETON 



posterior porLion, where they often take the form of prolonga- 

 tions, the extremities of whicli occasionally meet and enclose 

 what are called fenestrae ; but these are im- 

 important when compared with the features pre- 

 sented by the anterior part. 



4. The Pectoral Arch, or 



Shoulder -Girdle, consists of 



■•:.,_ three pairs of bones, the 



J'^^ ■■■::•. Coracoids, the Scapulae 



or Shoulder-blades, 



""■-,, and the Clavicles 



or Collar- 



bones, the last two usu- 

 ally coalescing in the 

 median line into a 

 V-shaped or U-shaped 

 Furciila (the well-known 

 "Merry-thought"); but 

 some group's, as 

 certain Parrots, the 

 clavicles are practically 

 ^ ^ absent, while in others, 



Fig. 3.— Skeleton of the Limbs and Tail of a Carinate ^^ Several Owls, they do 

 Bird. {The skeleton of the body is indicated by nnt nnito TK^ f i 



dotted lines.) F, digits; Fi, iibula; IIW, carpus; ^f ""■"'^- ^hc furcula 

 MF, tarsometatarsus ; MH, carpometacarpus ; OA, oftCn OSSifies firmlv 

 humerus ; 0«, femur ; Py, pygostyle ; ie, toracoid ; T;p,», fl,^ „ j. ■ 

 Ul, ulna ; Sch, scapula ; St, sternum, with its keel "^ '''^^ anterior por- 

 (Cr) ; T, tibiotarsus ; Rd, radius ; Z, Z^, digits of tion of the keel and in 

 loot. (From Wiedersheim. ) -n, , ^ . ' "■ -i^J- 



„ ,,, ,^ . ' J'^ei/ata, Didus and the 



Matitae, the coracoids and scapulae are fused together. 



5. The Anterior Limbs, or Wings, are composed of the 

 Humerus, or upper arm - bone, the Ulna and Eadius (mak- 

 ing the fore-arm), the Carpus or wrist, the Metacarpus and 

 Digits, corresponding with the hand and fingers. The first of the 

 three metacarpals bears the PoUex, or thumb, with one or two 



