INTRODUCTION 



lilTno has not felt the urge to explore the quiet lagoon, the 

 sandy beach, the coral reef, the Isolated sandbar, the wide muddy tidal 

 flat, or the rock-bound coast? How many rich harvests of specimens do these 

 yield the collector from time to time? This volume is intended to answer 

 at least some of these questions. 



From the viewpoint of the biologist, artist, engineer, or 

 craftsman, shellfish present lessons in development, construction, symme- 

 try, harmony and color which are almost unique. To the novice an acquaint- 

 ance with these creatures will reveal an entirely new world which, in addi- 

 tion to affording real pleasure, will supply much of practical value. 



Life is indeed limitless and among the lesser animals this 

 is particularly true. A mighty pattern is being woven into which signifi- 

 cantly fits the smallest organism, which under the microscope reveals for 

 a moment its importance in the lengthy chain. Some of these units may dis- 

 appear from the surface of the earth and be replaced by others. This con- 

 stant weaving, building up a little here and tearing down some there, con- 

 stitutes what some may designate as evolution. Adaptation does not neces- 

 sarily express the conformity of a species to its environment. Local con- 

 ditions influence the mode of life to a very marked extent. Sustenance, 

 pigmentation, and amount of lime available for shell building are reflected 

 in succeeding generations. Different conditions in various localities 

 often result in abnormal size, stunted growth or peculiar color patterns. 

 Allowance should be made for these influences where peculiar conditions pre- 

 vail. Giants or dwarfs may readily be recognized. 



Each individual reader or student may actually assist in 

 adding to the knowledge of American shells. With the span of human life 

 comparatively short it is better for individuals to specialize, more or 

 less, rather than attempt to cover a very broad field. Intensive and reg- 

 ular local observations will prove more productive than those carried on 

 some distance away. The English realize this and their tiny island has 

 not yet revealed all of its secrets. The broad American continent needs 

 naturalists in every community to complete the census of animals and 

 plants. Long stretches of coastline upon the Atlantic and Gulf have never 

 been intelligently worked for shells. The collector will eventually wander 

 into new fields and find the opportunities for recording data endless. This 

 service consists, in one way, of making careful records of the habits of 

 even the common species. A well-known authority estimates that eventually 

 a hundred thousand mollusks will be known, against the sixty thousand odd 

 species which have already been described. These figures are given not to 

 discourage the beginner but to suggest the work in which he may assume a 

 share. 



It will be noted that not all the species of a given genus 

 appear together in the illustrations contained in this volume. With a 

 shell in hand for comparison it will be best to run through all the plates, 

 at first, until a figure approximating the specimen is found. Then refer- 

 ence to the text will permit comparison with the diagnoses of the group. 

 The individual species may be studied in turn the last of all. With a lit- 

 tle knowledge and practice it should soon be possible for the reader to as- 

 sign the larger shells fairly close to their actual position in the text. 



