Dr T. B. Reynoldson of the Department of Zoology, University College of North Wales, Bangor, found some large enchytraeids on the shores of the Menai Straits. He suspected that it was an undescribed, or at least a rare and interesting species, and kindly sent six specimens to me for further study. I find that the specimens are indeed to be ascribed to a new species, which is here named Lumbricillus reynoldsoni, in recognition of the finder's prominent work on the ecology of Lumbricillus lineatus Mull, and Enchytraeus albidus Henle.