MOLLUSCA OF MICHIGAN— WALKER. 441 



In addition to the two papers by Mr. Currier, already referred to, the 

 following local lists have been published: 



In 1872-3, Mr. Sidney I. Smith published ''A Sketch of the Invertebrate 

 Fauna of Lake Superior." 



In 1876, Mr. C. E. Beecher and myself compiled for the Ann Arbor Scien- 

 tific Association a list of the species found in that vicinity. 



And in 1893, I published "A List of the Shells of the Saginaw Valley," 

 based upon the collection of the late Dr. George A. Lathrop, and in 1896 a 

 ''Report upon the Mollusca Collected in the Vicinity of Charlevoix." 



In 1904, Mr. A. G. Ruthven pubhshed a list of the Mollusca of Ontonagon 

 county. And in 1905 in connection with the writer a further list of the 

 Mollusca of Ontonagon County and those of Isle Royale. 



The following papers have also been published by the writer on special 

 subjects of investigation. 



''The Distribution of the Unionidap in Michigan'' (1898), "The Terres- 

 trial Mollusca of Michigan" (1899) and "The Distribution of Polygyra in 

 Michigan" (1905); in 1905 a synopsis of the fauna as known at the present 

 time. 



In addition to these papers Avhich are devoted entirely to the shells of the 

 state, many scattering references to our fauna are to be found in the writings 

 of nearly all the prominent conchologists of this county. A full list of these 

 will be found in the bibliography appended to the concluding portion of 

 this paper. 



In 1894, the Michigan Academy of Science was organized and the very 

 considerable advances made in knowledge of the molluscan fauna of the 

 state within the last decade have been due, to no small extent, to the in- 

 fluence of this organization in stimulating hearty co-operation among its 

 members. The Section of Conchology was organized in the spring of 1896 

 with thirteen members. Steps were taken at once to prepare a complete 

 census of the Michigan Fauna. This involved: 



First. The compilation of all the records of every species known or cited 

 from the state up to that time, and: 



Second. Such additions from year to year as the field work of the mem- 

 bers might supply. 



The first requirement was accomplished in due time and the second has 

 been very faithfully carried out by most of the members. The work of the 

 Section has naturally developed in two lines: 



First, The authentication or disproof of the actual occurrence within the 

 state of all species previously accredited to our fauna and the addition of 

 such new species as were found. 



Second, The extension of our knowledge as to the distribution of the dif- 

 ferent species through the state. 



The result of this systematic endeavor has, in the aggregate, been very 

 large, 'and the completeness of the present catalogue is to no small extent 

 due to the members of the Section. 



The growth of our knowledge of the molluscan fauna of the state during' 

 the sixty-six years which have elapsed since the first catalogue was published 

 is shown by the following synopsis of the number of species listed in catai- 

 logues of Sager (1839), Miles (1860), Currier (1868), DeCamp (1881), Walker 

 (1894), and Walker (1905). In arranging it all those species, whose occur- 

 rence in the state is considered doubtful for reasons hereinafter given, and 

 all synonyms and varieties have been eliminated. 



