133 
THE ORDER OP PERCHERS, OR 
INSESSORES. 
The remaining portion of tins Yolume will contain 
the major part of the different families of the 
Perchers belonging to Western Africa, commencing 
with the conic-hilled tribe ( Conirostres J, and pro- 
ceeding to the tooth-billed groups forming the tribe 
of Dentirostres. 
WHITE-BACKED CROW. 
Corms leuconolus, Swains. 
PLATE V, 
Glossy purplish black ; interscapular collar, and middle of the 
body, white. 
The old ornithologists considered that nearly all 
those Crows which were about the size of that of 
Britain were mere varieties of that bird; and so 
little were they regarded, that they were not deemed 
to be worth separate descriptions. This error, how- 
ever, has long been dissipated, and it is now found 
that a considerable number of distinct races, in dif- 
ferent parts of the world, have thus been passed 
