SHUFELDT. ] OSTEOLOGY OF THE TETRAONIDA. 691 
the conformation it gives to that bone in the adult are shown in Plate 
VII, Fig. 58, and itis marked 8in Fig. 59 of the young Sage Cock. - 
The metacarpal for the index digit is likewise detached, although even 
at this early date it begins to assume a likeness to the bone as found in 
the adult. 
Medius and annularis metacarpals are also distinctly free, and their 
size and position faithfully portrayed in the figure alluded to above. 
The prominent process on the rear and upper third of the shaft of me- 
dius of the adult is now found only in cartilage in the younger indi- 
vidual. The rest of the bony part of the pinion is familiar to all of us; 
it consists, in the adult “Cock of the Plains,” as in all Grouse and the 
Ortygine, of a tribedral phalanx for the first metacarpal, constituting 
theindex. Wehave found this phalanx in Meleagris and Ortyx bearing 
a well developed claw, covered with horn as in the ungual phalanges of 
of the feet; this is also the case in Numida and Pavo, and there is hardly 
a doubt but that this is the case with all of the American Galline, and 
in this respect they agree with this class of birds of the Old World. Two 
more phalanges are devoted to the medius metacarpal, the superior joint 
or phalanx having the usual expanded blade, with the long free and 
pointed finger-bone below; and finally the smallest phalanx of all, freely 
attached to the distal end of the third metacarpal or annularis. 
These bones are non-pneumatic, as are all the bones beyond the bra- 
chium in the Tetraonide. ; 
Of the Pelvis and the Pelvic Limb.—After what we have said and seen 
in regard to the dilatory manner in which originally primitive elements 
in these birds anchylose, and only after the lapse of weeks condescend 
to amalgamate and form the confluent bones and cavities that occur in 
the major division of the Class, we must not be surprised to find the 
same routine and a like tardiness exhibited in the pelvic heemal arch, or 
the pelvis, and its appendage the lower extremity. 
A glance at the figures illustrating the condition of the bones in ques- 
tion, of birds from one to two months old, will convince us at once 7aat 
the rule still obtains; in them we find the sutures among the ossa in- 
nominata still ununited, and the three bones of either side of the pelvis 
independent, and easily detached from each other about the cotyloid 
ring. 
In the young chick of Centrocercus (Plate VIII, Fig. 62), the ilium 
is a Scale-like bone that rests against the sacral vertebre. The pre- 
acetabular portion is excessively thin and delicate, and at this period 
constitutes the longest and widest part of the bone; its: border mesiad 
bears no vertebral impressions, but is sharp and brittle ; the outer margin 
is slightly rounded; this condition increasing as we near the diminutive 
acetabulum, where it is the stoutest. The distal margin, imperceptibly 
continuous with the inner, presents a convex curve anteriorly; the in- 
cluded surface viewed from above has a general concave aspect, espe- 
cially near its central portion. As we proceed backwards, however, it 
gradually becomes convex, to rise over the region opposite the cotyloid 
ring to form the general convex surface of the post-acetabular portion. 
The distal margin of the bone is nearly square across, and does not 
extend as far back as the ischium, the two being bound together at this 
age by cartilage, which has been removed in the plate. The outer and 
exterior margin of this division of the bone is rounded and fashioned 
the homologue of the pisiform as found inthe Mammalia; such at present being by no 
means the case, and all things considered, I have taken the liberty to change its name 
to the pentosteon, it being the fifth bonelet in the avian wrist. The same argument 
ase ne urged against the unciform, but I had nothing to do with the christening 
of that bone. 
