134 
WHITE BACKED CROW. 
oyer. Whenever a wide difference of geographic 
range is accompanied by others of colour, we may 
generally assume that species haring some simi- 
larity are nevertheless distinct. 
These observations are applicable to the present 
bird. It has much resemblance to that figured by 
Le Yaillant under the name of Le Corneille a sca- 
jmlaire blanc ( Ois. d'Af. ii. PI. 53. J, from the 
southern extremity of this continent ; but if it were 
the same, we can hardly suppose he would have 
represented the bird as having the black extending 
no farther than the chin, when in this it occupies the 
whole of the neck and breast. Until, therefore, 
w T e have further evidence upon this point, we ven- 
ture to consider the Senegal bird as distinct. The 
black part of the plumage is very glossy ; and the 
feathers of the head and throat are pointed. The 
wings are very long, and reach to the end of the 
tail ; this latter is rounded, having the feathers 
very broad and mucronate. 
The form is strictly typical Total length, about 
18 inches; bill, from the gape, 2j% ; wings, 13 1 ; 
tail, 7 ; tarsus, 2. 
