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XXXVI. — Observations on some Species of the 
Genus Mergus. 
By James Wilson, Esq. 
{Read March 1823.) 
Among many recent elucidations of the more difficult 
points in ornithology, certain species of the genus Mergus 
appear to have continued almost in the same state of ob- 
scurity ever since the days of Willoughby. This has not 
been owing to the want of zeal or to any negligence on the 
part of naturalists, because the subject has greatly occupied 
the attention not only of those who have published on the 
British ornithology, but of foreign authors. In our own 
country it has been especially investigated by Hey sham, 
Latham, and Montagu, although certainly not with any 
very definite or satisfactory results. The jwant of success 
in a matter to which so many acute men have applied, them- 
selves, must therefore be sought for in some peculiar cir- 
cumstances attending the history of the species. 
The Mergus castor^ usually called by us the Dundiver, 
was described by Linn^us as a distinct species. Some 
