144 THE FORAMINIFERA 



FAMILY 1. TEXTULARIDAE. Typically bi- or tri-serial ; often bi-, 

 rarely tri-formed. Genera Textularia, Def. Chambers in two rows, 

 alternating ; aperture an arched slit transverse to long axis of test at the 

 base of the inner wall of the final segment. Cuneolina, d'Orb. Ver- 

 neuilina, d'Orb. Triserial, with textularian aperture (Fig. 44, C). Tritaxia, 

 Keuss. Triserial, with a produced central aperture. Chrysalidina, d'Orb. 

 Triserial, with porous aperture. Bigenerina, d'Orb. Early chambers 

 textularian, later uniserial (Fig. 44, D). Pavonina, d'Orb. Arrangement 

 similar, but test fan-shaped and aperture porous. Spiroplecta, Ehrbg. 

 Early chambers piano-spiral, later textularian (Figs. 43 and 44, A-b). 

 Gaudryina, d'Orb. Early chambers triserial, later textularian. Valvu- 

 lina, d'Orb. Free or adherent, spiral, typically with three chambers in 

 each convolution. Clavulina, d'Orb. Early chambers triserial (valvuline), 

 later uniserial and rectilinear (Fig. 44, E). 



FAMILY 2. BULIMINIDAE. Typically spiral ; weaker forms more or 

 less regularly biserial, aperture oblique, more or less comma -shaped. 

 Genera Bulimina, d'Orb. Spiral, elongate, more or less tapering, often 

 triserial (Fig. 54). Virgulina, d'Orb. Much elongated, often biserial. 

 Bifarina, P. and J. Early chambers Bulimine or Virguline, later uniserial. 

 Bolivina, d'Orb. Biserial. Pleurostomella, Reuss. 



FAMILY 3. CASSIDULINIDAE. Test a Textularia-like series of alter- 

 nating chambers, more or less coiled on itself in a piano-spiral manner. 

 Genera Cassidulina, O'Orb. Ehrenbergia, Reuss. 



ORDER 6. Chilostomellidea. 



Test calcareous, finely perforate, polythalamous. Segments following 

 each other from the same end of the long axis, or alternately at the two 

 ends, or in cycles of three ; more or less embracing ; aperture a curved 

 slit at the end or margin of the final segment. Genera Ellipsoidina, 

 Seg. Chilostomella, Reuss. Allomorphina, Reuss. 



ORDER 7. Lagenidea. 



Test calcareous, very finely perforated, monothalamous, or consisting 

 of a number of chambers joined in a straight, curved, spiral, alternating, 

 or (rarely) branching series. Aperture terminal, simple or radiate. No 

 canalicular skeleton or canal system. 



FAMILY 1. LAGENIDAE. Test monothalamous. Genus Lagena, Walker 

 and Boys (Fig. 46). 



FAMILY 2. NODOSARIIDAE. Test polythalamous, straight, arcuate, 

 or plano-spiraL Genera Nodosaria, Lam. Straight or curved, chambers 

 circular in transverse section, aperture central (Figs. 45, A and B). Lingu- 

 lina, d'Orb. Straight, chambers oval in section, aperture a fissure. 

 Frondicularia, Def. Compressed, segments V-shaped (Fig. 45, C). Ehab- 

 dogonium, Reuss. Straight or curved, triangular or quadrangular in 

 section. Marginulina, d'Orb. Elongated, circular in section, aperture 

 marginal. Vaginulina, d'Orb. Elongated, septation oblique, aperture 

 marginal. Bimulina, d'Orb. Cristellaria, Lamk. Piano-spiral in part, or 



