* 
SHUFELDT. | OSTEOLOGY OF THE TETRAONID. 687 
general appearance goes. The common model is seen in Plate XII, Fig. 
87, Cupidonia; but observe even here in these closely-related fowls how 
habit still tells upon skeletal characteristics. The broad, and not deep, 
pneumatic U-arch of Cathartes becomes the long non-pneumatic, almost 
acute, V-arch of the birds we are describing; so, in view of being 
familiar with the habits of the Sharp-tailed Grouse and Sage Cock, 
need one be surprised to find in the fourchette of the first a depth of 4 
centimeters (omitting the inferior clavicular expansion), with an inter- 
space of 2.5 centimeters separating the superior articulating extremities, 
as compared with the bone in the second, where the depth is 6.2 centi- 
meters, and the interspace above only 1.7 centimetres. 
The bones of this arch are easily taken apart by maceration, and as 
has already been hinted they resemble each other very closely among 
the genera. The posterior angle between scapula and coracoid averages 
for the species about 60°, and among the Grouse the distal end of the 
shoulder-blade is usually found to overhang the fourth dorsal pleura- 
pophysis on either side; butin the California Quail these bones actually 
extend so far back as to overshadow the ilia for nearly a centimetre, 
they being proportionately narrow for their unusual length. This bone 
with the Grouse is only semi-pneumatic, its pneumaticity being confined 
to its coracoidal extremity, where the foramen is found in its usual site. 
The blade is thin behind, becoming stouter as it nears the glenoid 
cavity, sharp along its inner border, rounded without, clubbed at its 
pelvic end, and turned gently outwards along its entire length. Ante- 
riorly it contributes about one-third of the surface for the humeral joint, 
the coracoid the remaining two-thirds, while the acromial process within 
reaches forward barely to touch the clavicle, forming, as it does so, 
the usual interscapulo-coracoidal canal. , 
These bones are narrow in Bonasa and in C. canadensis, more curved in 
Lagopus, and very stout in Centrocercus, a good medium being seen in 
the Pinnated Grouse (Plate XII, Fig. 85). 
In Meleagris, they have their distal extremities cut square across, and 
reach back slightly beyond the pelvis. These bones in this species are 
also very stout and strong, and present the interesting variation in hav- 
ing a long pneumatic foramen on the superior aspect of each just beyond 
their glenoidal ends; this feature is not present in Pavo. They are ex- 
ceedingly narrow and long in the Massena Partridge. 
The Coracoids are quite stout bones, but devoid of any marked 
peculiarities; after leaving their sternal beds they extend upwards, 
forwards, and outwards, the furculum governing their distance apart 
at their upper ends. The glencidal procss is extensive, and rises 
nearly as high as the head of the bone; the clavicular process is faintly 
bifurcated, and curls over slightly towards the fellow of the opposite 
side. The shafts are compressed from before backwards, and soon 
dilate into broad expansions below; anteriorly one longitudinal muscular 
ridge marks the surface of the bone, while on the sternal aspect two or 
three very distinct ones occur. The inner angle of the dilated base 
nearly meets its fellow of the opposite side through the foramen, at the 
root of the manubrial process; from this corner outwards, for about 
two-thirds of the distance the surface is devoted to a curved articulating 
facet for the coracoidal groove, while the outer angle is tilted upwards 
and finished off by a distinctive little tubercle. On its posterior aspect, 
about the middle of the dilated part, a large, irregular pneumatic fora- 
men is found in all the Grouse, but seems to be absent in the Partridges. 
They are very large in Meleagris, at the same time being elliptical and 
