i883.j PROCEEDINGS OF UNITED .STATES NATIONAL MUSEUM. 247 



this latter linger being narrow and solid; the little joint behind it ex- 

 tending rather more than halfway down its posterior border. 



Among the Swans the general plan of" the limb is the same, but the 

 humerus, an exquisitely beautiful bone in these birds, is but very slightly 

 longer than the ulna. 



The skeleton of the piniou is quite as we find it iu the Dueks. 



I have yet to find a true Americau anserine bird that possesses a 

 pneumatic bone iu its pelvic limb. All the species before me entirely 

 lack this character. 



In Spatula the trocbanteriau ridge of the femur has a thick, curling- 

 crest on the autero-superior aspect of the bone, but at the summit it is 

 leveled down to the same plane with the articular surface. The head 

 is rather large and sessile and the excavation for the round ligament 

 shallow. 



We find the distal extremity unusually large; indeed, all the bony 

 structures that enter into a Duck's knee-joint are large and massive- 

 This is particularly the case with the condylar extremity of the femur 

 in Glaueionctta, where these prominences are powerfully produced be- 

 hind, and a wide and deep cleft splits the outer one for the fibular head. 

 In this form, too, a deep pit is found in the popliteal fossa. 



Eeturning to the femur of Spatula, we note that its shaft is nearly 

 straight, being marked by the usual muscular lines, while the pit just 

 spoken of is absent. The rotular channel extends slightly up the shaft 

 above the condyles, whereas in GJaucionetta this is not the case, and in 

 this Duck the femoral head is notably large and extensively excavated 

 on top ; the lower third of its shaft is somewhat bowed to the front and 

 a little twisted, recalling to our mind the power of that peculiar arch as 

 exhibited in such a marked degree in Urinator. 



The Spoon-bill, and I suppose other Ducks will show the same, has 

 an extraordinarily formed patella, being flat on top, wedge-shaped in 

 front, broad and concave behind, deeply excavated and arched below, 

 while across its anterior face it is profoundly slit in the oblique direction 

 for the tendon of the ambiens muscle. 



In the tibio-tarsus we find a large, flake-like, and jutting procnemial 

 crest, which curls toward the fibular side and ends abruptly high up on 

 the shaft. The ectocuemial crest is also turned outward, but is low and 

 thick. These prominences are but slightly elevated above the articular 

 summit of the bone, while in Olaucionetta they are carried up iu such a 

 manner as almost to rival the Grebe in this particular, having very 

 much the same form. 



The tibio-tarsal shaft in Spatula is straight, smooth, and subcylin- 

 drical. It affords at its outer side the usual ridge for the accommoda- 

 tion of the fibula. This is very long in the Garrot. 



At the distal extremity we find that the entire end is considerably 

 bent toward the inner side, a character it presents in many other Ana- 

 tidce. The intercondylar notch is for the most part very wide and shal- 



