No. 1.] NORTH AMERICAN PASSERES. 89 
and the carina a little deeper in proportion.!_ So, too, for all the 
Sparrows and Finches, the fundamental form is the same 
throughout,? and it is familiar to every tyro in zodlogy. 
These Blue Thrushes (e.g. in S. szalia) possess a scapula in 
their shoulder girdles of a very distinctive form, common to 
them and most true 7urdide@. The bone is of the usual passe- 
rine pattern, with its posterior fourth somewhat expanded, while 
the extremity is obliquely truncated from within, outwards, and 
the terminal apex, drawn out with a little point, is turned some- 
what inwards towards the mesial plane. 
The coracozd is comparatively a long bone with slender shaft, 
the sternal moiety of which latter always develops an osseous, 
wing-like expansion, that gradually increases in width from its 
commencement above, downwards. The head of the coracoid 
is crooked over toward the mesial plane, and is of tuberous pro- 
portions as in most all Thrushes. 
The os furcula is invariably of the U-shaped form, with its 
lower half gracefully and gradually curved towards the keel of 
the sternum; the lower midpoint supporting a conspicuous hypo- 
cleidium. The free ends of the limbs of the os furcula in Stalia 
are always enlarged, being laterally compressed, and when the 
bone is articulated zz sztu, they, on either side, are in contact 
with the head of the corresponding scapula. 
Being well known in so far as its skeletal features are con- 
cerned, it only becomes necessary to bear in mind the principal 
points in the osteology of the pectoral limb of Sialia. 
We are to observe the presence of the os humero-scapulare, 
and of the small sesamoid at the elbow-joint, common to most, 
if not all Passeres. 
Further, it is to be noted that the bones of this limb, as well 
as those of the pelvic extremity, are always non-pneumatic, 
though the pneumatic fossa of the humerus is invariably capa- 
cious, and to make it appear more so, the head of the bone curls 
over an adjacent concavity, juxtaposed to the first-mentioned 
one. At the lower or distal end of the humerus, an “ epicondy- 
loid process” is ever present, while the shaft of the bone is not 
1See my figure of the sternum of Merula migratoria in the second edition of 
Coues’ Key to North American Birds, p. 145, Fig. 58. 
2 For a Sparrow, see the figure of the sternum of one of these birds in Prof. M. 
Harbison’s Elements of Zovlogy, p. 34, Fig. 9. 
