136 
SENEGAL PIAPEC. 
of their generic characters is the proportionate length 
of the lateral toes once alluded to ; it is the in- 
equality of these toes which indicates that such birds 
are arboreal, while those, on the contrary, which hare 
these toes equal, and the middle one lengthened, are 
of ambulating habits ; or at least that they frequent 
the ground more than trees. Crypsirina, in this 
respect, is entirely arboreal, the lateral toes being 
unequal, and the middle ones short ; while in Pti- 
lostomus the tarsi are long and robust, the lateral 
toes equal, and the middle one fully lengthened. 
In these characters it agrees with all the sub-genera 
of Corvus, wherein we include the true magpies; 
but then the whole structure of the bill and nostrils, 
in our views of the family, decidedly places the 
present genus, as well as Crypsirina, in a totally 
different division of it. The only genus of this 
sub-family ( Glaueopinas ) which we have not yet 
seen, is that which should follow Ptilostomus on 
the other side of the circle, and constitute the 
tenuirostral type. 
From the circumstance of Le Yaillant having 
found this species to be migratory in Southern Africa 
(where it is seen either singly or in small flocks), 
there can be no doubt that it quits Senegal at certain 
seasons, along with the grakles herein described, and 
returns to Western Africa to breed. We infer this 
latter circumstance from having seen a young speci- 
men from Senegal, before it had quite gained its full 
wing-feathers ; it was much smaller, and the bill was 
red or flesh-coloured, tipt only with black. W e were 
