2 BULLETIN 104, UNITED STATES NATIONAL MUSEUM. 



to the entire development of such a genus as Haplophragmoides in 

 the Lituohdae. 



In the most primitive subfamily, the Spiroplectinae, the coiled 

 development is continued for a fairly long period, and makes up a 

 considerable portion of the test. This coiled stage also occurs in 

 both the microspheric and megalospheric forms, showing that this 

 subfamily is decidedly primitive and has not as yet become so 

 specialized as to lose the coiled stage in the megalospheric form. 

 In Spiroplecta, the only genus of this subfamily, the coiled develop- 

 ment is followed by a series of more or less numerous chambers ar- 

 ranged biserially. Spiroplecta in its stages of development recapitu- 

 lates the essential features of the Textulariidae — a proloculum, fol- 

 lowed by a closely coiled series of chambers, in turn followed by a 

 biserially arranged group. This sequence is the basis of the de- 

 velopment throughout the family, as will be shown, and is not an 

 exceptional character. 



In the Textulariinae, the typical genus of which, Textnlaria, may 

 be taken as an example, the same stages are shown, but are modified 

 by specialization and acceleration of development. The earlier 

 stages are either much reduced or are entirely skipped. Micro- 

 spheric forms of certain species of Textularia have been referred by 

 many later Avriters to Spiroplecta, 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 Spiro- 

 plecta 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 considerable coiled stage, and in which it usually 

 occurs in both forms, microspheric 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 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 de- 

 velopment in the microspheric form of at least one species. 



In the subfamily Verneuilininae 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 manipulate, 

 and the coiled series may be more common than many at first appear. 

 The expected modification — the return to the biserial condition of 



