8 SKELETON CHAP. 
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- 
Sch sented by the anterior part. 
Rs 4. The Pectoral Arch, or 
s,s. Shoulder-Girdle, consists of 
= three pairs of bones, the 
: .. Coracoids, the Scapulae 
Bie ( — = Ray s% “sx or Shoulder-blades, 
’ 
Dar 
“os and the Clavicles 
ae. or -@ Collare 
Lp 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 
V....yyp ™M some groups, as 
certain Parrots, the 
clavicles are practically 
me absent, while in others, 
Fig. 3.—Skeleton of the Limbs and Tail of a Carinate @S several Owls, they do 
Bird. (The skeleton of the body is indicated by not unite. The fureula 
dotted lines.) #, digits; Fi, fibula; HIV, carpus; : 
MF, tarsometatarsus ; MH, carpometacarpus ; OA, often — ossifies firmly 
humerus; OS, femur; Py, pygostyle; R, coracoid ; with the anterior por- 
Rd, ulna; Sch, scapula; St, sternum, with its keel 3 
(Cr) ; 7, tibiotarsus ; Ul, radius; Z, Z}, digits of tion of the keel, and in 
foot. (From Wiedersheim.) Fregata, Didus and the 
fatitae, 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 
