74 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. IX. 



General plumage, gray, or brownish gray; distance from tip of 

 bill to nostril, less than distance from nostril to eye (immature). 



Olor columbianus. 

 Whistling Swan. 



See No. 73. 



General plumage, gray or brownish gray ; distance from tip of bill 

 to nostril, more than distance from nostril to eye (immature). 



Olor buccinator. 

 Trumpeter Swan. 

 See No. 74. 



