The classification here used is practically that given in the 

 preliminary outline. It is based upon the known geologic his- 

 tory of the genera, upon the phylogenetic characters through a 

 study of much fossil material and finally by a study of the 

 ontogeny in very many microspheric specimens which show 

 the relationships much more definitely than do the megalospheric 

 specimens of the same species. 



There are so many institutions and individuals to whom I am 

 indebted for the gift or loan of material for study that to men- 

 tion them all would add pages to this volume. It may be suf- 

 ficient to say that without their co-operation this work could 

 hardly have been attempted. To my friends, Dr. Yoshiaki 

 Ozawa and Dr. T. Wayland Vaughan, I am under deep obliga- 

 tion for taking care of the difficult families of the Fusulinidae 

 and Orbitoididae, two families of great importance on which 

 very intensive researches are now being carried on in many 

 parts of the world. 



To my daughter. Miss Alice E. Cushman, I am under great 

 debt for taking excellent care of manuscripts and proofs, and to 

 Miss Margaret S. Moore for painstaking work in making the 

 drawings for the half-tone plates. 



Under the various headings will be found many of the com- 

 mon facts in regard to the present day knowledge of foramini- 

 fera, their uses and their classification. Keys are given which 

 it is hoped will prove useful to teachers, students, and those en- 

 gaged in economic work. A bibliography of important works is 

 also given for the sake of those who may wish to consult the 

 literature on the subject. There are still a number of genera 

 that are not sufficiently well known so that their position in the 

 classification can be accurately determined and a number of 

 them are left out until their genotypes can be studied in detail. 

 To try to place them at present from our present inadequate 

 descriptions or figures without studying the actual types would 

 only lead to confusion and thus it has been thought wisest to 

 leave these until some one may actually study the types. 



