The British Guiana Museum. 251 
As will already have been seen in the description of 
the two preceding orders of birds, the bills and feet 
furnish most useful characters for the purposes of 
classification ; and this will be still further evidenced in 
the following orders. Until within recent years, these 
were the main characters w r hich were taken into account 
in arranging birds into primary groups, but the increase 
of knowledge as to the internal stru&ure of these 
animals, has in recent years necessitated considerable 
alterations in the old systems, though the alliances of 
many small groups are still but imperfectly understood. 
The old order Scansores, or climbing birds, included not 
only the parrots, but also the woodpeckers, the cuckoos, 
the trogons, the toucans and the puff-birds, in all of 
which two toes are turned forwards and two backwards ; 
but it is now known that, in spite of this formation of 
the foot, these birds have no close affinity to the parrots, 
but are much more closely allied to other forms such as 
the kingfishers, the swifts, the humming-birds, the goat- 
suckers etc., which were classed formerly with the 
thrushes, the shrikes, the finches, the cotingas and the 
creepers etc., as the order Insessores or perching birds. 
The old orders, Scansores, and Insessores, have there- 
fore been split up into three. The name Psittaci is 
given to the parrots and their allies, the name Picaria? 
to the woodpeckers and their allies, and the name 
Passeres to the thrushes and their allies. 
In connexion with the formation of the feet of birds, 
it might be worth while to notice that only the toes are 
ever really applied to the ground. The bones which 
correspond to the sole of the foot and the ankle-bones in 
man, become partially fused in all birds to form the long 
