Hi Dima, we received more feedback about a scientific name issue from a BHL user. Thanks for looking into this when you have time:
URL: http://www.biodiversitylibrary.org/search?searchTerm=Prostomum+marginatum
Searching for Prostomum marginatum brings up a hyperlink with two hits for Prostomum marginatum Leidy, 1847, but each of those three hits really points to Produxus marginatus, an insect (Prostomum is a flatworm)