OF the six species of Holothurians with shield-shaped tentacles (the Aspidochirotae) that are known to occur on the shores of the North Atlantic Ocean, two—H. obscura and H. agglututinata—were so shortly described by Le Sueur as to be still, strange to American naturalists; no definite statement as to the presence of a true, that is, aspidochirote, Holothurian in the British seas has ever made its way into any systematic revision or synopsis of the class.