FOKAMINIFERA OF NOETH PACIFIC OCEAN. 3 



case make up the greater part of the test, are biserially arranged. 

 The stages in the development are exactly the same, but there is a 

 difference in the proportion of each as usually occurs in the upward 

 step in the scale, the earlier stages being shortened and the later 

 stages coincidently shoved back and taking their place. In the 

 megalospheric form of the species, however (fig. 17), there is a larger 

 proloculum, followed at once by the biserially arranged chambers, 

 the coiled stage being entirely skipped. Microspheric forms of such 

 species of Textularia have been referred by many later writers to Spiro- 

 ]>h eta, but in the type species of Textularia both of these forms occur, 

 and if such a procedure were adhered to, the genus Textularia would 

 have to be made synonymous with Spiroplecta and the former used 

 as the older name, the latter being dropped. As used here, however, 

 Spiroplecta includes simply those species which have a very consider- 

 able coiled stage, and in which it usually occurs in both forms, micro- 

 spheric and megalospheric. 



In Textularia, it is only very rarely, so far as observed, that a 

 coiled stage occurs in the megalospheric form, and then in but a very 

 few chambers. It is obvious, therefore, that the microspheric form 

 of many species of Textularia has a coiled development in the young. 

 In the more specialized species, such as Textularia quadrilatera, 

 which should perhaps be removed from the genus Textularia, there 

 has been observed no coiled young in either the microspheric or the 

 megalospheric form, though the number of available specimens of 

 each form has been large. 



In this same subfamily have been included those other genera 

 which have essentially a biserial arrangement of the chambers, such 

 as Bolivina and Pavonina, and a biserial development followed by 

 a uniserial, as in Bigenerina. In this last genus there is a coiled 

 development in the microspheric form of at least one species. 



In the subfamily Verneuilininse, the typical arrangement of the 

 adult chambers is triserial instead of biserial, but here again there is 

 in the microspheric form of some species a coiled series of chambers 

 in the young. The specimens are much more difficult to manipu- 

 late, and the coiled series may be more common than may at first 

 appear. The expected modification, the return to the biserial con- 

 dition of the previous subfamily, takes place in Gaudryina, in some 

 species only in the last-formed chambers, in other species appearing 

 by acceleration of development early in the life history, the triserial 

 portion much reduced. In Clavulina there is a complete return to 

 the uniserial condition, but with the triserial character present in the 

 young. 



The subfamily Buliminina3, as here considered, includes the spiral 

 forms with a loop-shaped aperture, such as Bulimina and Virgulina, 



