176 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



from twenty-two to twenty-six. (The next in order are Coscoroha 

 Candida having 21, and Branta canadensis with 20, and of birds belong- 

 ing to other families, the long necked Plotns anliinga with 20 vertebnie 

 colli, and Plioeni copter us ^ in which I have found only 18.) 



The number of the dorsal vertebra' amounts to eight, and consequently 

 there are eight pairs of dorsal pleur apophyses, the first five usually sup- 

 porting epipleural appendages. The three last have no uncinate processes 

 as do likewise neither the two cervical ribs nor the sacral one. 



The body of the sternum is square, with the lateral margins quite 

 l)arallel, and not narrower at the hind 

 termination of the costal border, where 

 the last dorsal rib articulates, as in the 

 other Anatidce. (See figs. 1 and 2.) The 

 hind border, with two fyroportionally 

 shallow notches, their length makiiig as 

 a rule about one-sixth of the greatest 

 length of the sternum. The middle por- 

 tion of the end of the sternum usually 

 slightly sinuated. The crista sterni is 

 rather high, but the carinal angle does 

 not j)rotrude forward longer than the 

 short manubrium, the fore border of the 

 crista being more or less arched. In the one genus (Olor), the carina of 

 which is shallow for the reception of a long fold of the windpi])e, the 

 anterior margin consequently is double; in the other genera only a 

 little concave. The lower limit of the crista is slightly curved. The 

 greater portion of the lateral margin of the corpus sterni is occupied 

 by the costal border, from which eight hwmapophyses ascend to meet the 

 dorsal ribs, the free border behind being proportionately very short. 

 The pectoral ridge on the body of the sternum, defining the origin of 

 mttsculus pectoralis secundus, does not run 'parallel with the external 

 margin or to the end of the keel, as is the case in the other Anatidce 

 (figs. 3-5), but passes obliquely towards the middle, which it reaches 

 before the termination of the crista. This feature, however, is not 

 always equally marked. In one of the skeletons of the Olor columbianus 

 which I have examined, the course has some resemblance to that of 

 Coscoroba, not dismissing, however, its jjeculiar swanlike character. 



The clavicles form a broad, rather robust, U-shaped arch, except in 

 the genus Olor, where the lower end is bent upwards and backwards 

 to admit the fold of the trachea to enter the hollow keel of the breast 

 bone. 



The coracoids are rather short and very stout bones. The scapula is 

 proportionaUy short. 



The most marked feature in the osteology of the Swans, wherein 

 they differ from the other members of the family, and which character- 

 izes them as powerful flyers, seems to be the considerable length of 

 the humerus and antibracliium, these being almost of equal length* 



