486 DR. R. W. SHUFELDT ON [NoV. 16, 



extensors, just above the sole on the one side, and which passes 

 above the distal trochleae 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 bicarotidince normales, as defined by Garrod. 



I would remark, however, that the carotids come off from the 

 innominates 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 ilhistrate 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 Gentropus 

 phasianus among the Cuculidse that the rare condition of the 

 femoral artery being the main one obtains. 



0/ 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 Qeococcyx affinis (Ji*.Z.^. 1877, p. 312), and says 

 that it completely disappears in the adult. I can vei'ify 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 Centropodince. 



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. 



