2 BULLETIN 161, UNITED STATES NATIONAL MUSEUM 



illustrated by Miss Ann Shepard (plates 1-4, 7, 10, 16, 17, 21, 27, and 

 28) between 1936 and 1940. 



The completion of the task of identification, together with the 

 verification of all identifications, the writing of the text, and the 

 compiling of distribution and abundance tables, has been done by me. 

 In this task I have had the able assistance of Doris Low in compiling 

 tables and of Lawrence B. Isham, Scientific Illustrator, U.S. National 

 Museum, in illustrating the remaining species (plates 5, 6, 8, 9, 11-15, 

 18-20, 22-26). I also gratefully acknowledge the many helpful 

 suggestions received from various reviewers of the manuscript, in 

 particular those from Frances L. Parker of Scripps Institution of 

 Oceanography. 



In presenting the data in this final part, I have found it more 

 appropriate not to follow precisely the method used for the other 

 three parts. Because nearly all the species discussed are well known, 

 I have omitted formal descriptions of most of the species and have 

 included only brief comments on distinguishing characters, diagnostic 

 features, variability, probable ecologic, geographic, and stratigraphic 

 distributions, and sometimes phylogenetic relationships. 



Some of the species included here were described originally from 

 these same Albatross collections (Cushman, 1933b). For many of 

 these species the original figure is included on the present plates. 



In the intervening years since the publication of the third part of 

 this work, various circumstances have stimulated interest in the 

 Foraminifera of the tropical Pacific as well as in the classification of 

 the Order Foraminifera. There have resulted many changes in con- 

 cepts of generic relationships and in nomenclature. No effort is made 

 to conform precisely with any existent classification. The sequence 

 of genera is approximately that followed by the Cushman (1948) classi- 

 fication, with some minor exceptions occasioned by the separation of 

 the planktonic from the benthonic groups, and the separation of the 

 aragonitic from the calcitic groups. The families are grouped in two 

 main subdivisions: benthonic and planktonic. The benthonic fami- 

 lies are grouped into two subdivisions: calcitic and aragonitic. The 

 calcitic families include most of the genera. 



Another natural subdivision of the species included in this study 

 is whether or not the specimen was presumed to have been attached 

 during life. But such a natural subdivision is not capable of being 

 followed in arrangement of genera because it does not fall along generic 

 lines, nor even always along specific lines. This feature of probable 

 attachment is not always positively determinable but is subject to 

 interpretation. Most specimens of species belonging in the genera 

 Patellina, Rosalina, Neoconorbina, Cibicides, Planorbulina, Planor- 

 bulinella, and Acervulina were very likely attached during some part 



