68 
THE VOYAGE OF H.M.S. CHALLENGER. 
Test triserial (sometimes dimorphous), with simple;, pro- 
duced, central aperture, .... Tritaxia, Eeuss. 
Test triserial (sometimes dimorphous) with porous 
aperture, ...... Chrysalidina, d’Orbigny. 
Dimorphous ( Textularian ) forms. 
Early chambers Textularian, later chambers uni- 
serial and rectilinear, . . . Bigenerina, d’Orbigny. 
Early chambers small and Textularian, later 
chambers broadly arched and uniserial, form- 
ing a fan-shaped test ; aperture porous, . Pavonina , d’Orbigny. 
Early segments planospiral, later ones Textularian, Spiroplecta, Ehrenberg. 
Early segments triserial (Verneuiline), later ones 
Textularian ; aperture either Textularian or 
situated in a short terminal neck, . . Gaudryina, d’Orbigny. 
Test spiral, typically triserial, with three segments or 
rarely more in each convolution ; free or adherent ; 
aperture partially covered by a valvular lip, . Valvulina, d’Orbigny. 
Dimorphous ( Valvuline ) form. 
Early segments triserial (Valvuline), later ones 
uniserial' and rectilinear ; test generally either 
cylindrical or trifacial ; aperture valvular, . Clavulina, d’Orbigny. 
Sub-family 2. Buliminmse, — typically spiral ; weaker forms more or less regularly 
biserial ; aperture oblique, comma-shaped or some modification of that form. 
Test spiral, elongate, more or less- tapering ; often triserial, Bulimina, d’Orbigny. 
Test much elongated, with a tendency to become asym- 
metrically biserial, . . ... . . .... Virgulina, d’Orbigny. 
Dimorphous form. 
Early segments Bulimine or Virguline, later ones 
uniserial, . . . . . Bifarina, Parker & Jones. 
Test distinctly biserial, arrangement Textularian, . Bolivina, d’Orbigny. 
Test biserial : aperture large, usually arched or semicircular 
with a notch at the middle of the lower edge ; 
situated at the top of the nearly erect septal face of 
the last segment, . ., . . . Pleurostomella, Re uss. 
