216 The Molluscan Family Plauorbidae 



In the sixty plates included in this appendix (plates 82 to 141), many 

 type specimens and other critically determined materials are figured, and 

 information as to the present whereabouts of these critical materials is 

 made available. In the members of the family Planorbidae, where syn- 

 onymy has been so involved and w^iere intergradations in shell characters 

 have been so confusing, the interpretation of range of individual vari- 

 ability by one who has devoted years to the study and had the singular 

 advantage of access to all the important collections, will be appreciated by 

 all naturalists who have the need for studying snails. 



For convenience of reference, the plates in the appendix are numbered 

 in direct continuation with the series of plates in the body of the mono- 

 graph. In the explanation of the plates, the repository of the figured speci- 

 mens is usually indicated by the following abbreviations: 



A.N.S. — Academy of Natural Sciences of Philadelphia 



B. — Frank Colhns Baker Collection 



C.A.S. — California Academy of Sciences 



M.C.Z. — Museum of Comparative Zoology, Harvard University 



U.C. — University of Colorado Museum 



U.I. — University of Illinois, Museum of Natural History 



U.M. — University of Michigan Museum 



U.S.N.M. — United States National Museum 



In connection with the foregoing list of repositories, it should be here 

 recorded that the Frank Collins Baker collection of fresh-water snails and 

 the specialized library accompanying it, after his death, was deposited in 

 the United States National Museum. This was in keeping with his ex- 

 pressed desire. It should be further explained that the collections attributed 

 to the University of Illinois are designated by two series of letters. Those 

 'U.I.' entries having the letter 'Z' preceding the accession numeral are in 

 the zoological research collections of the Museum of Natural History in 

 the University of Illinois. Paleontological specimens, indicated by inser- 

 tion of the letter 'P' immediately before the accession number, are now 

 deposited in the Paleontological Collections of the Illinois State Geological 

 Survey, in Urbana, Illinois. 



Citations of magnification in the explanation of the plates are usually 

 only approximate. In final preparation of the cuts, it was in many in- 

 stances unavoidably necessary to make slight modification of the author's 

 indicated amount of reduction from the original plates so as to conform 

 to the available page size. 



In listing the names of the species in the explanation of plates in the 

 appendix, Mr. Baker placed the name of the author of the species imme- 

 diately after the specific name and frequently gave no indication by the 

 use of parentheses in instances where the si~)ecific name was recombincd 

 with a generic name other than that to which the species was originally 

 ascribed. It should be recalled that the preliminary draft which he pre- 

 pared was never finally edited by him. Through the very generous cooper- 

 ation of a number of the most widely recognized American authorities in 

 the study of the Mollusca, the use of parentheses for author names has 

 been carefully checked. Some errors or inconsistencies may yet be found 

 because the literature is extremely scattered and there are no compre- 

 hensive check lists of the species of Planorbidae. 



As previously explained, the manuscript for the section in which Mr. 

 Baker had expected to provide full descriptions of all species and varieties 



