viii PREFACE. 



tirely new. It is believed that teachers will appreciate the 

 absence of those hackneyed illustrations which have too long 

 done service in text-books on the subject. 



To those especially interested in the study, many figures 

 are given which have never before been published, even in 

 scientific works, as, for example, the rare Lymncea mega- 

 soma, Lymncea ampla, Ptyelus lineatus, and many others. 



I desire here to express my thanks to Dr. A. S. Packard, 

 for looking over the pages relating to insects, and to Dr. H. 

 Hagen, Mr. Samuel H. Scudder, Prof. H. H. Straight, Prof. 

 Theodore Gill, Prof. A. J. Cook, and Miss Maggie W. 

 Brooks, for important specimens for illustration ; and to the 

 firm of Russell & Richardson, Boston, who, with the interest 

 of personal friends, have attended to the proper engraving 

 of my drawings. I am also deeply indebted to Prof. E. L. 

 Youmans, Mr. John M. Gould, and Mr. Henry W. Swasey, 

 for valuable suggestions and advice ; and, finally, I have to 

 express my gratitude to the publishers of this book, who 

 have, with unbounded liberality, left the entire matter of 

 illustration in my hands. 



E. S. M. 



SALEM, MASS., March 12, 1875. 



