No.2.] SHUFELDT ON NORTH AMERICAN TETRAONID^. 339 



In the old and matnre 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 ex- 

 tremity of the metacarpus, and the mode of articulation is the same. 

 This we know to be, first, a free, six-sided, unev^en bone, the scaphoid, 

 articulating chiefly with the distal extremity of the radius and the 

 metacarpus. This is the scapho-lunar of my former x^apers, and we retain 

 the application here ; it is also the radiale of Prof. Edward S. 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 carj^al and metacarpals ; this is the tdnare 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 scapholunar 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 carpaJe 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 bj^ cuneiform ; this is the nneiform, 

 (Plate YII, Figs. 57 and 59, z). 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 ; it is 

 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 

 pisiform. The manner in which it eventually joins the metacarpus and 

 the conformation it gives to that bone in the adult are shown in Plate 

 YII, Fig. oS, and it is marked 8 in 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 ui)per 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 



