Structural And Systematic Conchology Vol 2

Author : George W. Tryon
Publisher :
ISBN 13 : 9781332154524
Total Pages : 56 pages
Book Rating : 4.1/5 (545 download)

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Download or read book Manual of Conchology; Structural and Systematic, Vol. 2 written by George W. Tryon and published by . This book was released on 2015-08-04 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Manual of Conchology; Structural and Systematic, Vol. 2: With Illustrations of the Species; Zonitidae Animal protected by a spiral, heliciform shell, within which it is completely retractile; tail provided with a caudal mucuspore; 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 simple, 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. The jaw also is not ribbed, unlike most Helices, and the dentition differs. Externally, the animal is at once distinguished from Helix by the presence of a mucus-pore. There are some pulmoniferous mollusks having Zonitoid shells, whilst their soft parts place them in Helicidse, and vice versa. The animals of most of the species, however, are entirely unknown to science, and we are thus reduced to analogies of the shell in determining their systematic position. On the side of the Vitrinidae the relations of both animal and shell are quite as intimate, the group Otesia, for instance, which at the last moment I decided to include in the latter family, being made a member of the Zonitidae by Pfeiffer, Fischer and other good authorities. The Vitrinid mantle-lobes exist in a modified form in some of the groups of the present family. 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."