22 Mr. Swainson on the Typical Perfection 



genus. To this and to the curled tail of the tame duck, we 

 shall presently advert. 



Having now reached what appears to be the typical form 

 of Boschas, we see that nature, as usual, again departs from it. 

 The bill of the Mallard is throughout more depressed than that 

 of the common Teal. This depression, in fact, from being 

 greater than that of the Gad wall, or of the Pintail, obviously 

 assimilates more to the Shoveller. The affinity, however, ap- 

 pears remote, since the laminae of the Mallard are concealed, 

 while those of the Shovellers are conspicuously projecting. If, 

 therefore, the affinity was immediate, it could only be demon- 

 strated by a species having the bill of the common Duck but 

 with the laminae projecting. Now such a species is actually 

 the blue winged Teal of North America, in which these laminae 

 project nearly as much as in the Gadwall, while the upper 

 mandible exhibits that peculiar sinuosity towards the base 

 which is seen in no other ducks besides the Shovellers. If this 



affinity required any further support, it is placed beyond doubt 

 by the fact mentioned in the ' General History of Birds,' that 

 the plumage of the New Holland Shoveller, excepting the 

 white facial crescent, is precisely the same as that of the blue 

 winged Teal, the very bird which thus unites the subgenus 

 Boschas to that of Anas, and completes the circle of the whole 

 group. 



Zoological circles, however, if founded in nature, rest upon 

 much better testimony than mere opinion. I have attempted 

 to prove, in the forthcoming volume of * Northern Zoology,' 

 that the variation in animal structure is regulated by certain 



