XII. 

 FOREWORD 



FOR ALMOST A QUARTER OF A CENTURY, Frank Collins Baker 

 had been engaged in the preparation of detailed descriptions of the 

 species and critical evaluation of the synonymy of the Planorbidae 

 of the Western Hemisphere. This study was the natural outgrowth of the 

 long years of detailed morphological studies which led him to the evalua- 

 tion of anatomical detail as expressed in the broader phases of taxonomy 

 in the main body of the present volume. The second volume in this series 

 was to have treated the species of the Planorbidae in a manner similar to 

 his treatise on another large and important family of fresh-water snails, the 

 Lymnaeidae. Though published in 1911, his volume on the Lymnaeidae of 

 North and Middle America after more than thirty years still stands as the 

 leading taxonomic and distributional study of the lymnaeid snails of the 

 Western Hemisphere. 



Though such a program of study involved intimate familiarity with the 

 voluminous, scattered literature and wise interpretations of matters of dis- 

 puted priority and synonymy, these labors paled into insignificance when 

 compared with the self-imposed task of dissecting and microscopically 

 studying representatives of all the species available through the well- 

 recognized repositories of collections. To these customary sources were 

 added large quantities of material from individuals throughout the world 

 with whom kindly cooperation had established intimate personal and pro- 

 fessional contacts. Large numbers of dissections and long series of shells 

 gave opportunity for bridging the gap between the earlier field of Con- 

 chology and the newer science of Malacology to both of which Mr. Baker 

 had made notable contributions. As he reached final decisions on the 

 validity and synonymy of the species in the various genera, he prepared 

 photographs of the shells or of original drawings of the type specimens 

 wdien shells were not available. These photographs he arranged as plates 

 and for each he prepared a detailed descriptive legend. He had com- 

 pleted plates illustrating the shells of the genera HeUsoma, Carinijex, 

 Parapholyx, Planorhula, Menetus, Drepanotrema, Tropicorbis, and Ta- 

 phius. In his office at the time of his death were hundreds of photographic 

 prints of other genera and species intended for use in this monograph. 

 Some of these he had so marked and keyed with numbers that it has been 

 possible to assemble six additional plates which are included at the end of 

 the series. With this inclusion, all of the genera which he apparently 

 intended to figure are included though many of the species are not por- 

 trayed in the detail which he established in those earlier parts which he 

 had completed. The explanations of plates 136 to 141 are compiled from 

 rough pencil notes and must be accepted as the author's tentative arrange- 

 ment of work in progress which might have been changed somewhat in 

 the final editing. 



Some of the species not included in the plates of the api:)endix have 

 representative shells figured on plates 72 to 81 of the illustrations for the 

 body of the monograph. However, these figures are usually of only the 

 type species in each genus and do not carry out the plan of comprehensive 

 comparisons set for the second section of the monograjih as originally 

 projected by the author. 



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