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9 Introduction This work is intended as a guide for the identification of land snails and slugs of the Pacific Northwest, for use by biologists and other interested individuals who wish to identify most species in the field or laboratory without the necessity of dissecting the animals or sending them to a genetics laboratory. While not all species can be positively identified without the aid of dissection or molecular analysis, with this guide and some practice, most specimens should be recognizable to species. If a more exact identification is required, the specimens can be forwarded to a malacologist or genetics laboratory for further study. However, interested biologists and students of nature will find a large degree of satisfaction in observing and identifying these animals for themselves, and there is a definite need for such guides to identification of the lesser-known animals. It has long been the practice to dissect gastropods in order to determine their phylogeny and even to confirm certain specific taxa. In today’s taxonomy, analysis of the organism’s DNA is now complementing the study of anatomy. Both of these disciplines are important to the overall understanding of relationships between species and other taxonomic groups, but they are best left to the specialists. In many instances, even DNA analysis fails to answer all of the questions, and current taxonomy often uses groups of closely related clades instead of classes, orders, or groups of species. Analysis of variations in DNA requires a computer to sort out findings; thus the study is enhanced. But such necessary technology need not constrain the ability or the interest of the naturalist in the fieldwork of conservation. It is hoped that this guide will be a useful tool, enabling field biologists and other students of nature to continue working in the front lines of natural resource management and conservation. May we never lose the fascination that led us to these explorations, or the curiosity that continues to attract young and old alike to these essential fields of study. Mollusk Diversity Mollusca is the second largest phylum of animals on earth, exceeded only by Arthropoda, which contains the insects, arachnids, crustaceans, and other groups of jointed-legged invertebrates. Most of the better-known classes of mollusks occur in marine environments and include such diverse groups as the polyplacophorans 10 Land Snails and Slugs of the pacific northwest (chitons), the bivalvia (clams, oysters, mussels), the scaphopods (tooth or tusk shells), the gastropods (snails, abalones, limpets, sea slugs), and the cephalopods (octopus, squid, cuttlefish, nautilus). Although only two of these classes occupy the aquatic and terrestrial habitats of inland North America, most people are surprised at how diverse and abundant these animals are. The two classes of inland mollusks of the Pacific Northwest include four orders of Gastropoda (snails and slugs) and two of Bivalvia (freshwater mussels or clams). Our study is limited to the terrestrial gastropods, composed of land snails and slugs that inhabit the Pacific Northwest region of the United States, with four salt marsh inhabitants from the Pacific Coast also included. Those four are usually considered marine species, but inhabit areas that are not regularly inundated (see the introduction to the taxonomic list for more details); they are often omitted from books on seashells as well as from those on inland species. For this work, the Pacific Northwest is defined as the entirety of the states of Washington, Oregon, and Idaho, and the part of Montana west of the Continental Divide. Because the ranges of many species are poorly understood, and because extensions to the known ranges are continually being discovered, other species are included that are not known to occur within that area but which occur near its periphery. Land and Freshwater Mollusks of the Pacific Northwest Phylum Mollusca Class Bivalvia (Pelecypoda)—clams and mussels Order Heterodonta—includes Corbiculidae and Sphaeridae (Asian clams, pea clams, and fingernail clams) Order Schizodonta—includes Unionidae and Margaritiferidae (freshwater mussels) Class Gastropoda—snails, slugs, and limpets Subclass Eugastropoda—gill-breathing aquatic snails; aperture closed with an operculum Order Neotaenioglossa—mostly marine and aquatic snails; some salt marsh inhabitants Subclass Pulmonata—air-breathing snails and slugs; operculum lacking Order Basommatophora—mostly aquatic snails and limpets; in this work, one salt marsh species and one species of land snail Order Stylommatophora—land snails and slugs introduction 11 The Importance of Understanding and Identifying Mollusks Mollusks belong to the second largest phylum in the animal kingdom, which indicates how important they are in the ecology of the earth...


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