The present report is the result of a preliminary survey of the triclads of Michigan. Within the limited time at my disposal it was not possible to cover the entire territory of the state evenly. Field collections were made mainly within a one-day radius of the Biological Station of the University of Michigan on Douglas Lake, near Cheboygan, and in the vicinity of Ann Arbor. Considerable areas of the Lower Peninsula as well as most of the Upper Peninsula could not be included in the study.