1883.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 243 



This latter bone has its shaft much compressed from before, backward, 

 while its sternal extremity develops an unusual expansion, the infero- 

 external angle of which is truncated. 



Anas discors agrees in its pectoral arch, in the main, with the one 

 just described for the Broad-bill. It has, however, a rudimentary hypo- 

 cleidium present. 



This latter feature is entirely absent in Glaucionetta, where the fur- 

 cula is very strong and its \J very broad. Otherwise the bone is gen- 

 erally marked by all the characters it bears in the Ducks. The blade 

 of the scapula in Glaucionetta is much arched, and shorter and broader 

 than it is in the Teals. The coracoid presents nothing peculiar, having 

 much the same form that it has in Spatula, though it agrees with the 

 Teals in having a comparatively longer shaft. 



Aside from its greater size, Olor possesses a scapula very like that 

 bone in Glaucionetta. The Swan has its coracoid, however, very short and 

 thick-set, and does not at once suggest to us its family relations, though 

 a moment's study is sufficient to trace the modifications and resem- 

 blance. The unique form assumed by the fnrcula of this stately fowl 

 is well known to us. Its clavicular heads are long drawn out to termi- 

 nate posteriorly in sharp points. Moreover, the bone is highly pneu- 

 matic, the foramina being found well up on the outer aspect of either 

 limb, in a longitudinal excavation that there occurs. These clavicular 

 limbs gradually approach each other as they descend, and when they 

 come close to and opposite the middle points of the anterior and ver- 

 tical borders of the tracheal entrance to the sternum they are reflected 

 upward, and unite as a U arcn in the median line just beneath the 

 manubrium. The anterior aspect of this secondary arch is convex, 

 while behind it is much concaved, especially at its highest point, where 

 a small circumscribed pit occurs. The object of this modification of the 

 fourchette in the Swan is to permit the tracheal loop that enters the 

 carina of the sternum a passage-way, but the requisition of the entire 

 arrangement is one of those problems in anatomy which, I believe, 

 still awaits a final solution. 



The sternum affords another instance of skeletal likenesses between 



Fin. 24. Left lateral aspect of sternum of Spatula clypeata .• life size. .Same specimen as before. 



the genus Spatula and the Teals; indeed, this bone in the latter genus 

 is to all intents and purposes the perfect miniature of the sternum of 



