A MONOGRAPH OF THE FORAMINIFERA OF 

 THE NORTH PACIFIC OCEAN. 



ROTALIID.E. 



By Joseph Augustine Cushman, 



Of the Boston Society of Natural History. 



INTRODUCTION. 



This fifth part of the work on the North Pacific Foraminifera deals 

 with the single family Rotaliidae. In its natural order this family 

 comes before the Nummulitidae which was the last family treated 

 in the fourth part but which was taken up there in order to better 

 balance the parts, as previously explained. 



The members of this family have been widely known and well 

 worked and the new species are not very numerous. However, in 

 some genera the species seem to be more or less localized and often 

 prove to be new. Such genera as Spirillina and Discorbis are very 

 apt to have new species wherever found. 



If the collections which were available for the present paper had 

 included a greater amount of material from shallow water of the 

 tropical portion of the North Pacific, there would undoubtedly have 

 been a larger number of new forms and a greater number of species, 

 as certain genera are especially abundant under such conditions. 



It is interesting to note again the occurrence of a considerable 

 number of really tropical species up to the southern coast of Japan, 

 as has been mentioned in previous parts. 



In order to have for comparison original figures of many of the 

 species where later authors have included widely differing forms, a 

 series of outline figures has been introduced in the text adapted 

 from the type figure of the species whenever practicable, otherwise 

 from typical figures of subsequent authors. 



SYSTEMATIC TREATMENT. 



A systematic presentation of the family follows, the arrangement 

 of the data being the same as in preceding parts of this monograph. 



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