With the two fine Bourliere books on the market (The Natural History of Mamopals and Mammals of the World, the latter largely photographic -- both published by Knopf), it is hard for anyone outside the field of zoology to differentiate the Sanderson book and its market, from the others. Sanderson's name in the popular field provides an entering wedge. The list of contributing photographers includes some of the best names in the field. The classifications, intended to direct the book towards a lay market, follow the position on the ""family tree"" as done in the American Museum of Natural History. Extinct forms are excluded -- 19 main orders and 59 subdivisions are recognized.