Abstract
Metacercariae from Limulus polyphemus developed to sexual maturity in white mice and golden hamsters and are descr. as M. limuli. Morphologically they are very similar to M. claviformis but bionomic features seem to preclude their allocation to that sp. The genus Microphallus (=Spelophallus Jagerskiold, 1908) is discussed. In agreement with Cable and Kuns (1951), the family Maritrematidae Baer, 1943 is not accepted.