220 
ANAS VALISINERIA. 
general whiteness of its plumage. A short comparisO'J 
of the two will elucidate this point : The canvass-bac)'' 
measures two feet in length, by three feet in exteoh 
and when in the best order we'ighs three pounds an“ 
upwards. The pochard, according to Latham 
Bewick, measures nineteen inches in length, and thirf'^ 
in extent, and weighs one jiound twelve or thirtef'' 
ounces. The latter writer says of the pochard, “ tj'** 
Jtluinage above and helou’ is n'hollv covered with prettij^ 
freckled slender dusky threads, disposed transversely 
close set, zigzag lines, on a pale ground, more or 1*^ 
shaded off with ash a description much more a))plica)'| 
to the Inrd lignred beside it, the red head, and whi'^''' 
very probably is the sjjccies meant. In the figure of t*''’ 
pochard given by Mr Bewick, n ho is generaHy corn't* 
the hill agrees very well with that of our red head ; b''' 
is scarcely half the size and thickness of that of 
canvass-hack ; and the figure in the Plnnches 
corresponds in that respect with Bewick’s. In shotb 
either these writers are egregiously erroneous in th*-’*^ 
figures and descriptions, or the present duck 
altogether unknown to them. Consideriun- the latt‘'' 
supposition the more probable of the two, I ha'*'’ 
designated this as a new species, and shall proceed 
detail some particulars of its history. 
The canvass-hack duck arrives in the United Stat*”; 
from the north about the middle of October, a f'”' 
descend to the Hudson and Delaware, but the g^*^ , 
body of these birds resort to the numerous rivej^ 
belonging to and in the neighbourhood of the Chesapea‘'‘’ 
Bay, particularly the Susquehaunah, the Patajis*-?’ 
Potou mac, and James’ rivers, which appear to be the' 
general winter rendezvous. Beyond this, to the sou*^ 
I can find no certain accounts of them. At the Susq'*‘ 
hannah, they are called canvass-backs; on the Potowiu*’^ 
white-backs; and on James’ river, sheldrakes. They 8''^ 
seldom found at a great distance up any of these rivcf^’ 
or even in the salt water bay ; hut in that partici>'‘‘, 
part of tide water where a certain grass-like p'*''' 
grows, on the roots of n liich they feed. This pi*®'’ 
