A book for the identification of echinoids worldwide, mainly for shallow water species. The language is English, but the echinological terms are explained in a glossary in English, German and French. Beside detailed descriptions, an introduction is given into the morphology of the sea urchins; basic facts are dealt with: the general biology, the reproduction, growth, phylogeny and evolution. Some fossil sea urchins are shortly treated to illustrate evolutionary lines. The differences between clades, genera and species are worked out by tables, detailed sketches and enlarged photos. Additional support for easier identification is given by a key for major clades, and by 12 tables with the described species sorted according to their geographical distribution.