688 GEOLOGICAL SURVEY OF THE TERRITORIES. 
so open as to give a pretty fair view of the interior of the bone in some 
cases. 
The position of the united clavicles, or the free acromial extensions of 
the scapula, is shown for Lagopus in my drawing in Fig. 91. Something 
has been said about this bone already; we will add, however, that the 
superior ends always terminate by rather tuberous enlargements, smooth 
internally, but even as applied to the clavicular processes of the 
coracoids. The shafts are gently curved, of even calibre, and fall nearly 
directly downwards in some species, to be slightly expanded beneath in 
order to give better support for the large median dilatation below; this 
is triangular in outline, thickened in front, sharpened behind. In Ortyx 
this process is sometimes produced backwards, so as to nearly touch the 
sternum; this feature obtains, also, among some of the other Quails. 
The furculum of Meleagris is very different from that bone, as just 
described in general terms for the Grouse. It is V-shaped, to be sure, 
but for the size of the bird is extremely slender, the medium plate is 
smaller than we find it in many of the Quails; the superior halves of 
the limbs are dilated and exhibit excavations on their inner aspects, at 
the bases of which we find irregular groups of pneumatic: foramen; 
these limbs terminated above in truncate and thickened ends for artic- 
ulation with the remaining bones of the shoulder girdle. 
The furcula of Pavo and Numida are much more like the general type 
of the bone as found in the Tetraonide than the same bone in the Wild 
Turkey is. 
The bones of the shoulder girdle are all well advanced in ossification 
in the young chick, 
but do not develop 
ee 
their distinctive 
markings untila bird 
is pretty well along 
\ in age; this applies 
more particularly to 
muscular lines on the 
shafts, the base of 
the coracoids, and 
the clubbed extrem- 
ities of the scapule. 
In Bonasa, where we 
noticed how the body 
of the sternum was 
narrow like the 
Quails, we find also 
the median process 
of the united clavi- 
cles produced back- 
wards towards that 
bone. This Grouse’s 
skeleton, in fact, 
‘seems to have the 
greatest tendency Partridge-ward over any other of the North American 
Tetraonide. 
The free ossicle of the shoulder-joint, the os huwmero scapulare, is not 
present in any of these birds; a firm piece of inelastic cartilage seems 
to supersede it and fulfill a like function. 
The humerus (Plate VII, Fig. 57, H—Figs. 60, 61; also Plate X, Figs. 
Lagopus albus. 
