Nomenclature of the Foraminifera. 95 



vexity of the septum, and thus becoming terminal. In this way 

 it takes the form of a vertical slit-like aperture (generally with- 

 out a margin) in Grammostomum (a compressed Textularia) both 

 in the monomorphous and dimorphous forms, and especially in 

 the large individuals. 



Ehrenberg^s Proroporus (as illustrated by Reuss, Sitzungsb. 

 Akad. Wiss. Wien, vol. xl. p. 231, pi. 12. fig. 5) is an elongate 

 Textularia with its aperture terminal or nearly so. 



In Gaudryina and the sandy Sayrina the aperture is gene- 

 rally more or less margined and terminal. In Vemeuilina 

 the later cells have the aperture more and more axial ; the ter- 

 minal chamber in large specimens having a central aperture, 

 generally unlipped : these form Reuss's genus Tritaxia*. In 

 the bi- uniserial varieties, also, of Textularia the mouth becomes 

 central and pouting. 



A most complete confluence of all these Textularian forms, 

 whether varying in the mode of growth, the size and shape of 

 chambers, or position of aperture, is proved by the countless 

 intermediate modifications yielded by most sea-bottoms, fossil 

 and recent. 



The chief forms of Textularian growth may be thus enume- 

 rated : — 



Textularia proper. Biserial, with transverse aperture at the 

 base of the chamber. 



Bigerierina. Biserial, becoming uniserial (bi- uniserial) ; with a 

 terminal, round, pouting aperture. 



Grammostomum. Usually biserial, extremely compressed; with 

 simple slit-like aperture at the end of the chamber : occasion- 

 ally bimorphous or even trimorphous. 



Sagrina (in part : >S. rugosaf, D'Orb., sandy). Biserial and some- 

 times tri- biserial ; and then uniserial as far as one chamber ; 

 with a pouting, round terminal aperture. 



Gaudryina begins triserially (Verneuiline), and generally ends 

 biserially, the last aperture being Textularian ; but it runs 

 insensibly into the foregoing. Some Gaudryina are twisted 

 and Buliminoid. 



Vemeuilina. Triserial. V. dubia(Re\iss)=Uvigerina tricarinata, 

 D^Orb., takes in its last chamber a central aperture {Tritaxia, 

 Reuss) : another single chamber makes it Clavuline. In V. 

 dubia the aperture may be seen, in a series of specimens, to 

 creep up from the base of the cell to the top. 



Clavulina (part). Those Vemeuilina taking on a uniserial 



* Sitzungsberichte Akad. Wiss. Wien, 1860, vol. xl. p. 83. 

 t The other Sagrina (S. pulchella, D'Orb. For. Cuba, pi. I. figs. 23,24) 

 (biserial, ribbed, and not sandy) is a Uvigerina. 



