Carl Gottfried Semper (1832–1893) and the location of his type specimens of sea cucumbers

Carl Gottfried Semper (1832–1893), German naturalist, produced one of the most influential monographs in the history of sea-cucumber systematics (Echinodermata: Holothuroidea). This work, based on one of the most extensive collections of his time, introduced nearly a hundred taxa new to science. Unfortunately, Semper's collection subsequently became increasingly fragmented, and many of his types soon became considered as lost. We trace the history of Semper's holothuroid collection and report the location of many of the purported missing types.