A new monotypic genus Peosidrilus is established for the marine tubificid P. biprostatus n. sp. from New Jersey and North Carolina. The species is characterized by its possession of cylindrical atria ending in large, protrusible penes, two pairs of pedunculate prostate glands, paired spermathecae, and bundles of penial setae. Peosidrilus appears closely related to Phallodrilus Pierantoni, 1902.