THE ANATOMY OF BIRDS.— OSTEOLOGY. 147 
The Clavicles, or Furculum (Lat. clavicula, a little key: furculum, a little fork ; 
figs. 56, 59, cl), or the clavicular arch, are the pair of bones which when united together form 
the object well known as the “‘ merry-thought” or ‘‘ wish-bone,” corresponding to the human 
“ eollar-bones.” They lie in front of the breast, across the middle line of the body like a V 
or U; the upper ends uniting as a rule both with scapula and coracoid. For this purpose, in 
most birds, the ends are expanded more or less; such expansion is ¢alled the epiclerdiwm (Gr. 
eri, epi, upon; KAediov, kleidion, the collar-bone) ; in Passerine birds it is said to ossify separ- 
ately, and is considered by Parker to represent the procoracoid of reptiles. At the point of 
union below, the bones often develop a process (well shown in the domestic fowl) called the hypo- 
cleidium (Gr. ind, hypo, under ; fig. 59, he), supposed to represent the interclavicle of reptiles. 
The clavicles are as a rule present, perfect, anchylosed together, articulated at the shoulder; ina 
few birds anchylosed there; in several, there and 
with the keel of the sternum; in Opisthocomus there 
and with the manubrium of the sternum. In various 
birds, chiefly Picarian and Psittacine, they are de- 
fective, not meeting each other. They are wanting 
in Struthio, Rhea, Apteryx, and some Psittacida. 
Besides curving toward each other, the clavicles 
have usually a fore-and-aft curvature, convex for- 
ward. In general, the strength of the clavicles, 
the firmness of their connections, and the openness 
of the V or U, are indications of the volitorial or 
natatorial power of the wings. The end of the fur- 
culum is hollowed for a fold of the windpipe in the 
crested pintado (Owen). 
4. THE ‘PELVIC ARCH. 
The Pelvis (Lat. pelvis, a basin, fig. 60), is 
that posterior part of the trunk which receives the 
uro-genital, and lower portion of the digestive, vis- 
cera. It consists of the ‘ sacral” vertebre on the 
middle dorsal line, flanked on each side by the bones 
of the pelvic arch, which supports the hind limb. 
In vertebrates generally the pelvic basin is com- 
pleted on the ventral aspect by union (symphysis; 
Gr. ctv, sun, together ; duais, growth) of the bones 
from opposite sides. Excepting only Struthio, which 
has a pubic symphysis; and Rhea, which has an 
ischiac symphysis just below the sacral vertebre, 
the pelvis of a bird is entirely open below and 
behind; each pelvic arch anchylosing firmly with 
the sacral vertebree to form a roof over the viscera 
above named.‘ This sacro-iliac anchylosis is com- : ; 
monly coextensive with the confluence of the many Pin eerste tit sean ius aieeneoe 
vertebree which make the ‘‘sacrum” of ordinary RB. W. Shufeldt, U.S.A. dl, dorso-lumbar vertebra 
language, that i, from the frst dorso-lunnbar to the {2andineudingthe tae nee belo a, te 
Jast uro-sacral. The whole roof-like affair looks are the true sacral vertebre; us, urosacral verte- 
something like a keelless sternum inverted. The PF® (opposite the five oval black spaces; 7, ilium 
Z : Z a) Is, ischium; P, pubis; ob, obturator foramen. 
pelvic arch of each side consists of three bones, iliam, The arrow flies into the acetabulum. 
