SYSTEMATIC ARRANGEMENT 55 



Test trochoid, at least in the young of the microspheric form, 

 usually coarsely perforate, when lenticular, with equatorial 

 and lateral chambers. 



a. Test trochoid throughout, simple, aperture ventral. 



(1). No alternating supplementary chambers on the 

 ventral side Family 33. Rotaliidae. 



(2). Alternating supplementary chambers on the ventral 

 side Family 34. Amphisteginidae. 



b. Test trochoid and aperture ventral at least in the early 



stages. 



(1). With supplementary material and large spines 

 independent of the chambers. 



Family 35. Calcarinidae. 



(2) . With later chambers in annular series or globose with 

 multiple apertures but not covering the earlier 

 ones Family 36. Cymbaloporettidae. 



(3). With later chambers mostly somewhat biserial, 

 aperture elongate, in the axis of coiling. 



Family 37. Cassidulinidae. 



(4). With later chambers becoming involute, very few 

 making up the exterior in the adult, aperture 

 typically elongate, semicircular, in a few species 

 circular Family 38. Chilostomellidae. 



(5). With chambers mostly finely spinose and wall can- 

 cellated, adapted for pelagic life, globular forms 

 with the last chamber completely involute, aper- 

 tures umbilicate or along the sutures. 



Family 39. Globigerinidae. 



(6). Early chambers globigerine, later ones spreading 

 and compressed Family 40. Globorotaliidae. 



c. Test trochoid at least in the young, aperture peripheral 



or becoming dorsal. 

 (1). Mostly attached, dorsal side usually flattened. 



Family 41. Anomalinidae. 

 (2). Later chambers in annular series. 



Family 42. Planorbulinidae. 



d. Test trochoid in the very young, later growing upward. 

 (1). Later chambers in a loose spiral. 



Family 43. Rupertiidae. 



(2). Later chambers in masses or branching, highly 



colored Family 44. Homotremidae. 



e. Test trochoid in the very young of the microspheric form, 



chambers becoming annular later, with definite equa- 

 torial and lateral chambers, often with pillars. 



Family 45. Orbitoididae. 



