We report new records of the Clam Shrimp, Caenestheriella gynecia Mattox 1950, from three localities in the Hudson Valley of New York and one locality in northeastern New Jersey. All of our specimens were collected in puddles on dirt roads. The New Jersey specimens have meristics that are well within the range of Caenestheriella Daday 1915; however, the eastern New York specimens resemble those reported from Massachusetts with meristics that are closer to Cyzicus Audouin 1837. We hypothesize that C. gynecia was established as a parthenogenetic species due to an unlikely dispersal event in the western part of its range and has migrated eastward since the last glacial maximum. Dispersal of this species may occur by wind, in the gut of birds, or stuck to animal feet or fur, or to vehicles. We recommend that C. gynecia be treated as rare and vulnerable to extinction throughout its range unless demonstrated otherwise
