FORAMINIFERA 353 



Test trochoid throughout, simple; aperture ventral 



No alternating supplementary chambers on ventral side; 

 fossil and recent Family 32 Rotaliidae 



Genus Rotalia Lamarck (Fig. 161, g) 



Alternating supplementary chambers on ventral side; fossil 

 and recent Family 33 Amphisteginidae 



Genus Asterigerina d'Orbigny (Fig. 161, h) 



Test trochoid and aperture ventral in young 



With supplementary material and large spines, independent 

 of chambers; fossil and recent. . .Family 34 Calcarinidae 



Genus Calcarina d'Orbigny (Fig. 162, a) 



AVith later chambers in annular series or globose with multiple 

 apertures, but not covering earlier ones; fossil and recent 

 Family 35 Halkyardiidae 



Genus Halkyardia Heron-Allen et Earland (Fig. 162, 6) 



With later chambers somewhat biserial; aperture elongate in 



the. axis of coil; fossil and recent 



Family 36 Cassidulinidae 



Genus Cassidulina d'Orbigny (Fig. 162, c) 



With later chambers becoming involute, very few making up 

 the exterior in adult; aperture tj^pically elongate, semi- 

 circular; in a few species circular; fossil and recent 



Family 37 Chilostomellidae 



Genus AUomorphina Reuss (Fig. 162, d) 



With chambers mostly finely spinose and wall cancellated, 

 adapted for pelagic life, globular forms with the last 

 chamber completely involute; aperture umbilicate or along 

 the suture; fossil and recent. . . .Family 38 Globigerinidae 



Genus Globigerina d'Orbigny (Fig. 162, e) 



Early chambers globigerine, later ones spreading and com- 

 pressed; fossil and recent. .. .Family 39 Globorotallidae 



Genus Globorotalia Cushman 



Test trochoid at least in young, aperture peripheral or becoming 

 dorsal 



