In regard to the external anatomy or topography of a bird, a system as little complicated as possible is desir able. The one presented in this work, while substantially the same as that usually adopted, and Offering no innova tions, is considerably simplified, thereby greatly facilitating the acquirement by the student Of a knowledge Of this essential adjunct of descriptive ornithology. It is believed also that the figures representing the typical forms Of color-markings, and Of egg — contours, and the concordant scale of different standards of measurement, will also be found Of great practical utility. The author has in every case endeavored to give the plainest possible definition Of a term consistent with accuracy. All expressions having reference solely to internal characters, and which therefore seldom if ever enter into ordinary descriptions of birds, have been ex cluded, though many anatomical 'and osteological terms occasionally employed in diagnoses Of the higher groups, and others pertaining to the general treatment Of the subject, are considered and carefully defined.