Excerpt from A Monograph of the Freshwater Univalve Mollusca of the United States: Including Notices of Species in Other Parts of North America Gasteropodous monoicous indperculate pneumobranchiate testaceous aquatic mollusca'; having a single pair of triangular or filiform contractile tentacles, the surface of which is covered with vibrillae, * and having the eyes at their internal base: the shells are thin in tex ture, of uniform tints, and with the margin of the aperture sharp. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.