PREFACE 



It has been many years since the students of the North American fresh- 

 water molhisca have had at their service a concise and complete synopsis of 

 the classification in general use. 



The several monographs published by the Smithsonian Institution of 

 VV. G. Binney and Prime in 1865 ^^^ Tryon in 1873, together with Lea's 

 last Synopsis in 1870, gave a very complete representation of the systematic 

 arrangement in use at that time. 



Tryon's "Monograph of the Fresh-water Mollusca of the United States," 

 a continuation of Haldeman's Monograph of 1842, did not include the 

 Pleuroceridse and did not add substantially to systematic classification. 



Since that time, although our knowledge on the subject has greatly in- 

 creased, there have been no general monographs published covering the 

 entire field and the recorded advances in classification are only to be found 

 in many scattered publications not always accessible to the ordinary 

 collector. 



Certain groups have, indeed, been studied monographically. Simpson's 

 monumental "Synopsis of the Naiades" (1900) followed by his "Descrip- 

 tive Catalogue" of 19 14, revolutionized the classification of that great group 

 and pointed the way to a natural classification that has since been greatly 

 elaborated by Ortmann in many scattered papers. 



Baker's elaborate "Lymnaeidse of North and Middle America" (1911) 

 marked another great advance in systematic classification. 



Sterki's recent "Preliminary Catalog of North American Sph^eriidje" 

 (1916) embodies the results of many years of careful study of that family 

 and is, it is to be hoped, but the fore-runner of a complete, illustrated mono- 

 graph of that most interesting, but difficult, group. 



With these exceptions, the many changes in systematic nomenclature 

 resulting from the investigations of many different workers have been 

 published piece-meal, as it were, and in many dift'erent publications. 



The need of a concise synopsis, showing the state of the science at the 

 present time as adopted by those who are most familiar with the subject, 

 has been met by the Museum of Zoology of the University of Michigan in 

 its endeavors to further the study of Natural History in the schools of the 

 state and Part I of this paper is an attempt to place before the amateur 

 student a summary of the classification of the fresh-water mollusca which 

 is in current use. It is to be understood, of course, that with our constantly 

 increasing knowledge, many changes will, undoubtedly, be necessary in the 

 future and are to be expected and hoped for. The arrangement here pre- 

 sented is what the compiler understands to be the state of the science at the 

 present time. 



Part II is an out-growth of a card catalogue that the writer has main- 

 tained for his own convenience for many years. In the last half century the 

 knowledge of our fauna has enormously increased, but the many new species 



