690 GEOLOGICAL SURVEY OF THE TERRITORIES. — 
convex distally, while the inner articulating surface beneath the ex- 
panded end of the radius is uneven and applied to the concavities and 
convexities of the free pair of carpal elements. 
‘ These bones among the Partridges and other Grouse, except in size, 
present to us no extraordinary departures from the description just 
given of Lagopus. This remark applies also to the Wild Turkey, but the 
wing-bones in this bird seem to be shorter in comparison with its gen- 
eral size. 
We do not believe there is a bird in our country that can offer us better 
facilities for the study of the bones of the carpus than the young of 
Centrocercus wrophasianus. Anchylosis of the various segments involved 
is exceedingly tardy, and it is not at all necessary for the student of 
this joint, that has puzzled so many comparative anatomists and orni- 
thotomists, to seek the primoidal ossicles in the very young chick, unless 
he desires to ascertain the points as regards priority of ossification of 
the carpal bones, a question we will evade here entirely, for these bones 
are quite distinct and easily detached in the bird at six weeks or more 
of age, such as we offer our reader in the plates. 
In the adult Sage Cock, the carpus has the appearance of this joint, 
as it is Seen in nearly all of the class where there are two free carpal 
bones, and the os magnum confluent with the proximal extremity of 
the metacarpus, and the mode of articulation is the same. This we 
know to be, first, a free, six-sided, uneven bone, the scaphoid, articulat- 
ing chiefly with the distal extremity of the radius and the metacarpus. 
This is the scapho-lunar of my former papers, and we retain the same 
name for it here; it is also the raciale of Prof. Edward 8. Morse, who 
has made such positive advances in the elucidation of the tarsus and 
carpus in birds. 
The second bone is the cuneiform, larger than the first, and engaged 
principally by the cubit, but having also a process and an articulating 
surface for the confluent carpal and metacarpals; this is the ulnare of 
Morse. 
These are the two carpals that remain free during life. 
We will now devote ourselves to the joint as observed in the bird at 
six weeks of age. We have no trouble in finding scapho-lunar and cunei- 
form whatever. At the summit of the second metacarpal there is found 
a concavo-convex segment, that is universally taken to be the os mag- 
num, termed also carpale by Morse (Plate VII, Fig. 59, om). It articu- 
lates anteriorly with the upper end of the index metacarpal, covers the 
entire proximal extremity of the second, and nearly or quite meets 
another bone behind that is grasped by cuneiform; this is the unciform 
(Plate VII, Figs. 57 and 59,2). It has the appearance of being a detached 
and bulbous extension of the third metacarpal, and is about the size and 
shape of an ordinary grain of rice, having a shallow concavity on its 
anconal aspect. 
There is yet one perfectly free and distinct bone to be observed; itis 
found on the inner aspect, very near the extremity of second metacar- 
pal, just below os magnum; it nearly meets unciform, and articulates 
with the process of cuneiform behind. This little segment is flat and 
very nearly circular, being applied by one of its surfaces against the shaft 
of the metacarpal, and held in position by ligaments. This segment we 
do not find described by any author known to us, and here call it the 
pentosteon.! The manner in which it eventually joins the metacarpus and 
'This little bone of the carpus, which I still believe was originally described by 
myself, was called in the first edition of this Monograph the pisiform. This name 
might lead the student into the belief that I considered it either the analogue or even 
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