° 1915 ] Johnson, A Four-winged Wild Duck. 469 



A FOUR-WINGED WILD-DUCK. 



BY CHARLES EUGENE JOHNSON. 1 



Plates XXV1I-XXIX. 



On November 18 last, the Zoological Museum of the University 

 of Minnesota received through Mr. James Ford Bell of this city, 

 a wild duck possessing a pair of supernumerary wings. The speci- 

 men had been shot by Mr. J. H. Stadon, of Minneapolis, a few miles 

 west of Wyoming, Minnesota. While in Mr. Bell's possession, 

 the specimen was examined also by the veteran ornithologist Dr. 

 Thomas S. Roberts. The anomaly was considered sufficiently un- 

 usual and interesting to merit detailed study and publication. 



Supernumerary parts in connection with the appendages of the 

 body occur not infrequently among both vertebrates and inverte- 

 brates. Among vertebrates they appear in a variety of forms, such 

 as supernumerary fingers and toes, tails, horns, mamma 3 , earlike 

 appendages, etc. There appear also the more complex anomalies 

 known as "double hands," and "double feet;" and more rarely 

 there is found an extra pair of limbs nearly entire in themselves, 

 attached in the vicinity of a normal pair, with more or less abnormal 

 condition of the girdle, but in a body in other respects normal. The 

 relative frequency of such abnormalities apparently varies in dif- 

 ferent groups of vertebrates. Bateson ('94) in his extensive work, 

 calls attention to the many cases of polydactylism for instance, 

 known in the horse, pig, and cat, and the complete absence of any 

 records for the ass and very few for the sheep and dog. For the 

 human species there is a rather extensive record of such cases. In 

 birds, according to the same author, the total number of cases 

 recorded is comparatively small. While in the domestic fowl 

 polydactylism is common, in other groups it is rare; in pigeons, 

 ducks and geese it does not seem to be known. 



In the literature accessible, I have found no record of any avian 

 abnormality similar to the case to be here described. Broom ('97) 



1 From the Laboratory of Comparative Anatomy of Vertebrates, Department 

 of Animal Biology, University of Minnesota, Minneapolis. 



