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FAMILY II—COLYMBIDZ. 
From the natatorial groups of the Anatida, distinguished, 
as we have seen, from the rest of that family by the flattened 
form of the body, the backward position of the legs, the 
shortened and concave wings, and by habits more decidedly 
accordant with a life on the ocean, we now pass on to the 
family of the Colymbide. Here we shall find the above cha- 
racteristics displayed in a still greater degree, and which, as 
contributing so essentially to the perfection of this mode of 
existence, render this family one of the typical divisions of 
the Order. In the birds which cumpose it, the legs are 
placed at the extremity of the body, with which they form 
an acute angle, acting, as it were, as propelling oars from 
the stern. The tarsi and feet alone are exposed and free; 
the tibia and femur being inclosed within the integuments 
of the abdomen. ‘The tarsus is remarkably thin, or laterally 
compressed ; and the feet (although large, and furnished with 
membranes) have the toes so articulated, as to fold into a 
very small compass when drawn towards the body after ma- 
king the necessary stroke, thus offering the least possible re- 
sistance in the water. The lobated hind toe possessed by the 
more aquatic ducks is still retained in this family, and, in 
some members of it, is joined to the inner toe by a small 
uniting membrane, shewing thus a connexion also with the 
Pelecanide. 'The contour of the body is oval, broad, and 
depressed, narrowing towards the neck, which is long and 
tapering. ‘The wings are short and concave, as well, or per- 
haps even better, adapted for aiding progression beneath the 
surface of the water, as through the air. The bill is strait 
and compressed, ending in a sharp point, and destitute of 
the cuticular membrane that envelopes it in the Anatide. 
From the backward position of the legs the individuals of 
