486 DR. R. W. SHUFELDT ON [Nov. 16, 
extensors, just above the sole on the one side, and which passes 
above the distal trochlez on the other. 
As we pass the muscles we have described for this limb in review, 
it will at once be recognized that the list is unusually complete. 
All the ordinary muscles of the thigh are present as found in birds, 
and all highly developed. In the leg marked specialization and 
organization are everywhere evident, while exceptional muscles are 
here, too, fully represented. 
This complexity by no means diminishes as we proceed towards 
the foot, for the arrangement of the tendons as they course down 
the tarso-metatarsus and the special musculature of this division of 
the limb is manifestly indicative of high organization. 
Finally, we have the complex insertional extremities of the intri- 
cate system above laid before us in the foot ; and the most exquisite 
examples of adaptation, compactness, and final requirements are to 
be seen throughout the structure on every hand. 
Notes on the Arterial System. 
Fortunately the evisceration that had been performed upon my 
specimen before it came into my hands has not injured the heart and 
great vessels. So by a careful dissection I am enabled to state that 
there are two carotids in Geococcyx californianus, and that their 
arrangement and the method of their branching at the base of the 
heart is normal. In other words, the bird in this respect is to be 
included with the Aves bicarotidine normales, as defined by Garrod. 
I would remark, however, that the carotids come off from the 
imnominates at points considerably further removed from the heart 
than that anatomist depicts them in his diagram of this condition. 
The branching is the same, however, and no doubt Mr. Garrod’s 
figures were intended to illustrate this point above all others, to 
which end they serve an excellent purpose. 
Turning to the arterial system in the pelvic limb, I find that the 
main artery of the leg is the sciatic. This agrees with the vast 
majority of birds, and, so far as I am aware, it is only in Centropus 
phasianus among the Cuculide that the rare condition of the 
femoral artery being the main one obtains. 
Of the Bursa Fabricii. 
As I said at the beginning of this memoir, Forbes has already 
called our attention to the peculiarity of form of this structure in 
the young of Geococcyx affinis (P.Z.S8. 1877, p. 312), and says 
that it completely disappears in the adult. I can verify this state- 
ment so far as the specimen before me is concerned, for in it this 
bursa is not present, while the region otherwise is characterized as 
we find it in the adults of the Centropodine. 
The Trachea. (Plate XLIII. figs. 3 and 4.) 
For the entire length of this subcylindrical tube, the osseous rings 
which compose it fail to meet in the longitudinal median line 
posteriorly. 
