SHUFFLDT.] OSTEOLOGY OF THE TETRAONIDA. 6389 
76, 77 of Cupidonia) of Centrocercus is so exceedingly regular that it 
could be well chosen as the type of that bone in all birds in which it is 
pneumatic. It is due proportion for the size of the bird to which it 
belongs, possessing the usual sigmoidal curves from lateral and superior 
aspects (we describe the bone in situ in the closed wing) in graceful, though 
not decided prominence. The head or proximal extremity, slightly bent 
anconad, displays the most usual points for examination about it; an 
extensive convex, smooth surface is seen for the glenoidal cavity, below 
it a deep notch, then the well-defined “ ulnar crest” or lesser tuberosity 
curling over a large sub-elliptical pneumatic foramen, thatis so patu- 
lous that the osseous trabecule and net-work are plainly seen at its base. 
The radial crest encroaches but very little upon the shaft, is quite stout, 
and only at its summit shows any disposition to curve over palmad. 
The shaft is smooth, elliptical on section thronghout its extent, and 
almost entirely devoid of any muscular markings or lines; it swells 
gently in the vertical plane as it approaches the distal end of the bone, 
upon which is placed the ordinary tubercles for articulation with radius 
and ulna. The inferior condyle, the internal of human anatomy, is the 
better developed of the two, and the ulnar tubercle is produced a little 
beyond the bone distally, while the oblique tubercle is brought down on 
the shaft. The olecranon fossa is rather shallow in the Grouse, being 
decidedly better shown among the Quails. There are no prominent 
points of difference in this bone among the Tetraonide, except in regard 
to size; Cupidonia, which has rather a heavy skeleton any way, the 
humerus is moderately robust in accordance. 
In the Ortygine the same characteristics are to be seen; but we discover 
in addition at the proximal extremity of the bone, on its anconal aspect 
between the greater and lesser tuberosities, a deep fossa that has a great 
resemblance to the pneumatic orifice externally, and of about the same 
dimensions, being only separated from that depression by a thin bony 
wall; it seems to be designed simply for muscular insertion, and has no 
communication with the general cavity of the hollow humeral shaft. 
The radius and ulna are also singularly typical in their avian char- 
acteristics, as might have been looked for after our remarks upon the 
bone of the brachium; their principal difference lies in their being non- 
pneumatic, although they are hollow like all long bones. 
In the right arm of Lagopus leucurus, which we have before us, care- 
fully dried, in its position of rest, with all the ligaments still attached, 
im situ, we find the radius to be unusually straight, in fact almost in line 
between the oblique tubercle of the humerus and the bone it meets in 
the carpus. Its shaft is nearly cylindrical, and shows a muscular line, 
upon an otherwise smooth surface, that travels along its proximal two- 
thirds beneath. Distally it overlaps the cubit by a transversely dilated 
extremity to articulate with its carpal bone. The head of the ulna is 
large, and betrays the fact that it belongs to a bird of considerable 
power of flight; the olecranon process is a blunt, tuberous apophysis, 
slightly bent anconad; the greater and lesser sigmoidal cavities are dis- 
tinet and fairly marked, particularly the former. 
The shaft of the bone is more than twice the bulk of that of its com- 
panion, decidedly convex outwards, the curve being greatest at the 
junction of the proximal and middle thirds; it is elliptical on section, 
the major axis of the ellipse being vertical. The muscular lines of the 
ulna are but faintly developed, as are the row of minute tubercles for 
the bases of the quills of the secondaries. 
Anteriorly the bone displays its usual trochlea head for its own carpal 
segment; this surface is bounded palmad by a sharp and even curve, 
44__ Hf 
