6 BULLETIN 161, UNITED STATES NATIONAL MUSEUM 



Family TEXTULARIIDAE 

 Subfamily Spiroplectammininae 



Genus SPIROPLECTAMMINA Cushman, 1927 



Spiroplectammina Cushman, Contr. Cushman Lab. Foram. Res., vol. 3, p. 23, 

 1927 ; Cushman Lab. Foram. Res. Spec. Publ. No. 1, p. 114, 1928. 



Textularia (part) Parker and Jones (not Defrance), Philos. Trans., vol. 155, 

 p. 370, 1865. 



Spiroplecta H. B. Brady (not Ehrenberg), Rep. Voy. Challenger, Zoology, vol. 9, 

 p. 376, 1884. 



Genoholotype. — Textularia agglutinans var. biformis Parker and 

 Jones. 



Test free, early chambers planispiral in both microspheric and 

 megalospheric forms, later ones biserial ; wall arenaceous with a yel- 

 lowish-brown cement ; aperture in the planispiral portion at the base 

 of the apertural face, in the biserial portion at the inner margin of 

 the chamber. Carboniferous to Recent. 



Out of all the Textularia group present in this collection from the 

 Pacific only millet ti seems to belong to this genus. At this time com- 

 ment may be made on the relationships of this genus to Textularia. 

 Doctor Lacroix has recently published a paper on the relationships 

 of these, seeming to show that " Spiroplecta wrightii " is the same as 

 " Textularia sagittula." He also comes to the conclusion that all 

 species of Textularia have a spiral beginning, and that the chambers 

 may have been displaced where they are not present. An examina- 

 tion of many species of this genus does not carry out this hypothesis. 

 There are forms that have been placed under Spiroplectammina in 

 which both the megalospheric and microspheric forms have plani- 

 spirally coiled chambers in the end. These have been included under 

 Spiroplectammina. There are, however, a great many species excel- 

 lently preserved both in fossil and Recent material in which the 

 megalospheric form does not show any trace of spiral beginnings. 

 These seem to be distinct from the former group. It may be noted 

 here also that certain of the species referred to Textularia evidently 

 have their relationship with Gaudryina, and the microspheric form 

 shows traces of a triserial beginning instead of a spiral one. From 

 a strictly phylogenetic point of view, these should be distinguished 

 from the other Textularia group having their beginning in a spiral 

 form. By acceleration of development the triserial stage has become 

 more and more restricted, and the biserial stage is taken on earlier 

 and earlier. This process may continue until the relationship with 

 Oaudryina is lost entirely, and there may be no possible way of dis- 

 tinguishing textularian forms developed from this source from those 

 that have developed from spiral beginnings. 



