Excerpt from Thesaurus Conchyliorum, Vol. 3: Or Monographs of Genera of Shells IN the following arrangement of species, I have endeavoured to bring together those most nearly resembling each other, to facili tate comparison. In doing this I have found the gradations so subtle as almost to defy any systematic division into defined groups. There are no single characters which can be depended upon with any certainty in determining the affinities and distino tions either of groups or species. It is more by the eye, taking in an assemblage of characters, and regarding the general appear ance, that they can be appreciated. Thus, although for conveni ence I have followed a prevailing custom in placing by themselves in groups nearly all the coronated species, yet there still remain some coronated species whose general characters forced me to place them in widely difi'erent groups, while some generally coro mated species present varieties in which the whorls are smooth. This is only one instance of what occurs with regard to almost any character that can be named, such as length of spine, graun lation, etc. Under these circumstances it is impossible to main tain perfect consistency as to retaining and proposing some spe cies and rejecting others. As the collector's great object however is to know the shells, I have preferred in most cases giving the species as they stand, stating the alleged differences, and leaving the final decision to individual taste. Thus, some eight or ten so called species of the textile group, are, to the best of my belief, mere variations of one type; yet I have admitted them in the cata logue, simply stating the points in which they are said to differ. 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.