NATATORES. 379 



Genus ERISMATURA, Bonaparte. 



The members of this gemis, although but few in number, 

 are found in Europe, Asia, Africa, America, and Austraha. 

 They are especially adapted for immersion, and for obtaining 

 their food from the bottom of the water rather than on its 

 surface. 



In Bonaparte's Classification these birds are placed next to 

 the Mergansers, and are raised to the rank of a family — Uris- 

 matiirida — comprising the following genera : Biziura, Thalas- 

 siornis, and Erismatura. I think, however, the Prince was 

 not justified in uniting Merganetta with them, which, in my 

 opinion, should be associated with the Mergansers. 



Sp. 594. ERISMATURA AUSTRALIS. 



Blue-billed Duck. 



Oxyura australis, Gould in Proc. of Zool. See, part iv. p. 85. 

 Erismatura australis, Eytou, Mou. of Anat., p. 172. 

 Boud-doo, Aborigines of the lowland districts of Western Australia. 

 Blue-billed Duck of the Colonists. 



Erismatura australis, Gould, Birds of Australia, foL, vol. vii. pi. 17. 



This bird would appear to be so limited in its habitat as to 

 be confined to the colony of Western Australia ; at least up 

 to this time it has not been discovered in any other part of 

 the country. Gilbert's notes inform me that it is never seen 

 in the rivers, either those communicating with the sea or 

 those of the interior, and that it is only found on the lakes 

 running parallel to and near the coast that are surrounded 

 with high reeds and tea-trees. Its general habits resemble 

 those of the Biziura lohata \ like that bird it possesses the 

 power of remaining under water for a great length of time, 

 and if closely hunted flaps along the surface without taking 

 wing. Its voice is a peculiar inward tone, which the natives 

 describe by saying, " it has no voice, but makes a noise with 

 its heart." 



