FORAMINIFERA OF THE ATLANTIC OCEAN. 3 



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 Clawlina there is a complete return to 

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

 young. 



The subfamily Bulimininae, as here considered, includes the spiral 

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

 the latter tending to assume a biserial arrangement. The test here 

 is hyaline and perforate. 



The subfamily Cassidulininae includes species which are like the 

 Bulimininae in their aperture, but which have a peculiar arrange- 

 ment of the chambers. These are biserial, but are secondarily coiled 

 in a helicoid spiral. In Cassidulina the species are either completely 

 involute, or in late growth are somewhat uncoiled. In Ehrenbergina 

 the uncoiling takes place early and little of the involute character 

 is seen. 



The Textulariidae as a whole are much more rich in ornamentation 

 and complex forms than are any of the preceding families. In 

 Bolivina and in some species of Bulimina, Ehrenbergina, and Virgvlina, 

 there is a considerable range of ornamentation, punctae, limbate 

 sutures, knobs or bosses, costae and spines being the most common 

 forms. On the whole, however, the ornamentation is simple and 

 uninteresting compared with that seen in the Lagenidae. 



Subfamily 1. Spiroplectinae. 



Test either coarsely arenaceous or calcareous, or even hyaline, the 

 early chambers following the proloculum closely coiled, the later 

 chambers biserial, occasionally tending to become uniserial in the 

 last developed chambers. 



This subfamily includes the single genus Spiroplecta, which in its 

 developmental stages connects the Textulariidae with the Lituolidae. 

 Its development is primitive in that the stages are seen in both the 

 microspheric and megalospheric forms of the species, and are of com- 

 paratively long duration. 



Genus SPIROPLECTA Ehrenberg, 1844. 



Spiroplecta Ehrexberg (type, aS. amerimna Ehrenberg), Monatsber. preuss. Akad. 

 Wiss. Berlin, 1844, p. 75. — H. B. Brady, Rep. Voy. Challenger, Zoology, 

 vol. 9, 1884, p. 375. — Chapman, The Foraminifera, 1902, p. 170. — Cushman, 

 Bull. 71, U. S. Nat. Mas., pt. 2, 1911, p. 4. 



Description. — Test with the early chambers close-coiled in both 

 the microspheric and megalospheric forms, later chambers biserial, 

 wall typically arenaceous. 



