THE ANATOMY OF BIRDS. — OSTEOLOGY. 
147 
The Clavicles, or Furculum (Lat. clavicula, a little key : furculum, a little fork ; 
figs. 56, 59, cZ), 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 
collar-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 called the epicleidium (Gr. 
eVi, epij upon ; icKeidiov, Meidion, 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- 
deidium (Gr. viro, hypo, under ; fig. 59, /ic), supposed to represent the interclavicle of reptiles. 
The clavicles are as a rule present, perfect, anchylosed together, articulated at the shoulder; in a 
few birds anchylosed there; in several, there and 
with the keel of the sternum ; in Opistliocomus 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 StrutMo, Mliea, Apteryx, and some Psittacidce. 
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" vertebrae 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. (Tvv, sun, together ; (f)v(Tis, 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 vertebrae, 
the pelvis of a bird is entirely open below and 
behind; each pelvic arch anchylosing firmly with 
the sacral vertebrae to form a roof over the viscera 
above named. This sacro-iliac anchylosis is com- 
monly coextensive with the confluence of the many 
vertebrae which make the ''sacrum" of ordinary 
language, that is, fi'om the first dorso-lumbar to the 
last uro- sacral. The whole roof-like afiair looks 
something like a keelless sternum inverted. The 
pelvic arch of each side consists of three bones, ilium, 
Fig. 60. — Pelvis of a heron [Ardea herodias), 
nat. size, viewed from below ; from nature by Dr. 
R. W. Shufeldt, U.S.A. dl, dorso-lumbar vertebrae 
to and including the last one, sc ; below sc, for the 
extent of the /arf/e blackspaces(oppositethearrow) 
are the true sacral vertebrae ; us, urosacral verte- 
brae (opposite the five oval black spaces ; II, ilium ; 
Js, ischium; P, pubis; oh, obturator foramen. 
The arrow flies into the acetabulum. 
