Abstract
The geographic distribution of extant irregular echinoids from the orders Spatangoida, Clypeasteroida, Cassiduloida, Holasteroida, Holectypoida, and Neolampadoida is described. Individual geographic ranges worldwide are illustrated in map form for 414 echinoid species. Tables provide general presence-absence information for all major oceans, classification schemes, and literature citations for each species. An alphabetic list of all species includes relevant synonyms and citations for each species. The most speciose echinoid orders, Spatangoida and Clypeasteroida, are abundant in the Indo-West Pacific and Caribbean. The former group and the Holasteroids also inhabit Antarctic and Arctic seas. All irregular echinoids show relatively high species numbers amongst many islands and island chain regions. The Holectypoida and Neolampadoida are represented by only three living species each.