Proterometra sagittaria has not been reported from locations other than streams in northern Ohio that discharge into the west end of Lake Erie. We have found the intramolluscan stages of this species in 28 to 30% of Goniobasis livescens collected from the Sandusky River within the city limits of Fremont, Ohio. In the summer of 1966 a large number of these snails were taken to UMBS at Douglas Lake. At the end of the summer studies, several hundred remained alive. They were dispersed into the Carp River immediately downstream from a U.S. Highway 31 bridge, approx. 2.5 miles N of Levering, Michigan. ... It is evident that a population of P. sagittaria has been established in this location.