In 1934 an intensive but unsuccessful search was made for the metacercariae of the Rhodometopa group of cercariae parasitizing Turritella communis Lamarck. Attention was concentrated on the vertebrate and invertebrate fauna of the Rame Mud, as Turritella has a patchy and circumscribed distribution in the Plymouth neighbourhood and is virtually restricted to a few small areas of ground in this region. The high rate of infection suggested that the metacercariae must occur commonly in some species found there, and the behaviour of the cercariae indicated that a fish served as second intermediate host (Rothschild, 1935, p. 169). This has now been proved.