502 Mr. N. A. Vicors on the Natural Affinities 
Anser, Bernicla, and Cereopsis, until it is superseded by the short 
necks of the more oceanic Anatida, which exhibit all the ex- 
pansion and capaciousness of throat observable in the typical 
Natatores. 
The distinctively marked character of the lobated hind. toe, 
which prevails among the latter groups of the family we have 
just quitted, conducts us to Podiceps, Lath., that commences the 
family of Colymbide, where the same character is strongly de- 
veloped. The difference between the bills of the types of these 
two families is softened down by the intervention of that of 
Mergus, which is intermediate between the broad and depressed 
bill of 4nas and the narrow and sharp-pointed bill of Podiceps. 
This last genus, in conjunction with Colymbus, Linn., from which 
it differs chiefly in the construction of the foot, composes the 
family of Colymbide. These two well-known groups, differing 
but little among themselves in external characters, form one of 
those normal groups of the order, where a deficiency is exhibited 
in the powers of flight by the shortness of their wings, and in the 
faculty of walking by the backward position of their legs. These 
deficiencies in the groups before us are compensated for by their 
capability of remaining for a length of time under water, and by 
their superior powers of diving. For this latter purpose the 
structure both of their wings and legs is admirably adapted: the 
former by their strength assisting them as oars under water, and 
by their brevity not interfering with their progress ; the latter, by 
their compressed and sharpened edge offering no resistance to the 
water as they are drawn up to effect the stroke which accelerates 
the movements of the bird. From their superiority in these cha- 
racters and powers, the birds themselves have obtained par excel- 
lence the name of Divers. In these particulars we may observe 
them to be united to the A/cade which succeed them, and from 
which they are chiefly separated by the presence of the hind toe, 
conspi- 
