colymbidæ

from The Century Dictionary.

• A family of short-winged, short-tailed, 4-toed swimming and diving birds, of the order Pygopodes, either containing all the loons and grebes; or
• restricted to the web-footed loons, and corresponding to the genus Colymbus; or
• transferred to the lobefooted grebes, and used as a synonym of Podicipidæ or Podicipedidæ (which see).