MANUAL OF CONCHOLOGY; STRUCTURAL AND SYSTEMATIC, VOL. 2

With Illustrations of the Species, ZonitidæAnimal protected by a spiral, heliciform shell, within which it is completely retractile, tail provided with a caudal mucus pore, jaw with a median inferior projection, not ribbed, the central tooth in the lingual ribbon is tricuspid, with the middle cusp long and narrow, laterals bicuspid, marginals acuminate, unicuspidate or bicuspidate.Shell usually heliciform and perforate or umbilicate, often thin, and more or less transparent, the lip of the aperture sim ple, neither reflected nor with thickened margin.The family thus defined includes several hundred species, usually considered Helices, but which differ from that group in the generally thinner, more translucent shells, the aperture with simple margin, the genuine Helices being generally thicker, and with the margin of the aperture either reflected or thickened Within.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis 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.