Out of a large number of diseased potatoes sent by a merchant to this Institute and to the Ministry of Agriculture Pathological Laboratory, Harpenden, suspected of eelworm disease due to Tylenchus dipsaci, only one tuber was found by Mr. Buckhurst of the latter laboratory to contain eelworms; all the others, although presenting a naked-eye appearance extremely like that shown by tubers attacked by T. dipsaci, were entirely negative. This tuber was sent to the writer for his opinion on the nema-todes living in it with the result that what appears to be a new genus has been found. It resembles members of the genera Tylenchus and Aphelenchus in that it has a mouth stylet with swellings at its base and might at first sight be mistaken for a representative of one of these genera, a fact which renders a description of it all the more necessary, but differs from them in several morphological details.