A MONOGRAPH OF THE FORAMINIFERA OF 

 THE NORTH PACIFIC OCEAN. 



MILIOLIDAE. 

 By Joseph Augustine Cushman, 



Of the Boston Society of Natural History. 



INTRODUCTION. 



This sixth and last part of the work on the North Pacific Foram- 

 inifera deals with the single family Miliolidae. By most writers this 

 family has been considered as very primitive on account of its ap- 

 parently having no pores in the test, but it has gradually been ascend- 

 ing in the scale. In the Challenger report it was the earliest family 

 considered, but has since by many writers been placed above the 

 arenaceous forms of the Astrorhizidae and Lituolidae. 



The discovery by several workers that the earlier chambers of some 

 of the highest genera of the family have a perforate test shows that 

 it developed from a perforate ancestry. The geological history of the 

 family is also rather conducive to the idea that it developed rather 

 later than other relatively highly developed types as the Num- 

 mulitidae, where Fusulina, one of the complex types, was characteristic 

 of the Carboniferous. The greatest development of the Miliolidae as 

 far as number of species and complexity of structure are concerned 

 seems to have been the late Cretaceous and early Tertiary. 



The present paper does not contain as many species as would be 

 the case were the present collections better represented by shallow- 

 water material, especially about the tropical islands of the area. 



PHYLOGENETIC DEVELOPMENT OF THE MILIOLIDAE. 



To d'Orbigny must be given the credit for the first critical study 

 of the foraminifera belonging to the Miliolidae. Previous authors had 

 described and named certain of the species, but very little attempt 

 had been made to determine the relationships of the various forms. 

 In his work in 1826 d'Orbigny ' recognized many of the still accepted 

 generic characters and to a certain extent their relationships. Under 

 the Foraminiferes, Order Agathistegnes, d'Orbigny grouped the 



1 Tableau m^thodique de la classe des Cephalopodes, Ann. Sci. Nat., vol. 7 1826, p. 245, etc. 



1 



