IV INTRODUCTION. 



tion so little, indeed, that any observations whatever 

 upon this subject will be of value, if carefully made. 



The classification adopted by Professor Leidy has been 

 followed in this book, and in the descriptions of genera 

 and species the variations from the original have been 

 very slight, and only such as have seemed advisable to 

 make up for the lack of illustrative plates, or, in some cases, 

 for the sake of brevity. It is believed that the descrip- 

 tions will, in most cases, enable the student to name the 

 specimens that he finds without the aid of figures. 



Those who possess copies of Professor Leidy's work, 

 and who have not made Rhizopods a special study, will 

 find this book a valuable adjunct a sort of key to the 

 larger ome; for the schematic synopses of genera and 

 species will serve to lead the observer directly to the 

 proper genus or species with a fair degree of certainty, 

 by a hasty observation of the more prominent character- 

 istics of the forms that may be discovered. 



The careful study of Professor Leidy's work, which 

 the preparation of this Synopsis has necessitated, has 

 served to increase our admiration for his ability as an 

 observer, and our appreciation of the great labor he has so 

 conscientiously performed. Apart from the pleasure which 

 an enthusiast always feels when engaged in his favorite 

 study, Professor Leidy must find his reward mainly in 

 his own knowledge of the lasting value of his book, and 

 in the satisfaction of having done his work so well. 



