SKELETON 



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

 tions, the extremities of which occasionally meet and enclose 

 what are called fenestrae ; but these are un- 

 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 

 :>, Coracoids, the Scapulae 

 X;\ or Shoulder-blades, 

 "X arid the Clavicles 

 . \ or Collar- 



-ME 



bones, the last two usu- 

 ally coalescing in the 

 median line into a 

 V-shaped or U-shaped 

 Furcula (the well-known 

 "Merry- thought"); but 

 in some groups, as 

 certain Parrots, the 

 clavicles are practically 

 absent, while in others, 



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



Bird. (The skeleton of the body is indicated by no t unite. The furcula 

 dotted lines.) F, digits; Fi, fibula; HW, carpus; .~ 



MF, tarsometatarsus ; MH, carpometacarpus ; OA, Olten OSSineS firmly 



humerus ; OS, femur ; Py, pygostyle ; R, coracoid ; w ith the anterior por- 



Ul, ulna ; Sch, scapula ; St, sternum, with its keel . r . 



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

 foot. (From Wiedersheim.) Fregata, Didus and the 



Ratitae, 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 Radius (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 Pollex, or thumb, with one or two 



