SYSTEMATIC ARRANGEMENT 53 



A KEY TO THE FAMILIES OF THE FORAMINIFERA 



I. Test wanting or of thin chitinous material, living forms in fresh or 



brackish water or in the ocean Family 1. Allogromiidae. 



II. Test wholly or in part arenaceous. 



A. Test single chambered or rarely an irregular group of similar 



chambers loosely attached. 



1. Test with a central chamber and two or more arms. 



Family 2. Astrorhizidae. 



2. Test without a central chamber, elongate, open at both ends. 



Family 3. Rhizamminidae. 



3. Test a chamber or rarely series of similar chambers loosely 



attached, with normally a single opening. 



Family 4. Saccamminidae. 



B. Test two chambered, a proloculum and long undivided tubular sec- 



ond chamber. 



1, Test with the second chamber simple or branching, not coiled. 



Family 5. Hyperamminidae. 



2. Test with the second tubular chamber usually coiled at least 



in the young. 



a. Test of arenaceous material with much cement, usually 



yellowish- or reddish-brown. Family 7. Ammodiscidae. 



b. Test of siliceous material, second chamber partially 



divided Family 15. Silicinidae. 



C. Test typically many chambered. 



1. Test with all the chambers in a rectilinear series. 



Family 6. Reophacidae. 



2. Test planispirally coiled at least in the young. 



a. Axis of coiling short, many uncoiled forms. 



Family 8. Lituolidae. 



b. Axis of coiling usually long, all close coiled. 

 (1). Interior not labyrinthic, Palaeozoic. 



Family 12. Fusulinidae. 

 (2). Interior labyrinthic. Eocene. 



Family 13. Loftusiidae. 



3. Test typically biserial at least in the young of the microsphere 



form Family 9. Textulariidae. 



4. Test typically triserial at least in the young of the micro- 



spheric form. 



a. Aperture usually without a tooth, the test becoming 



simpler in higher forms. . .Family 10. Verneuilinidae. 



b. Aperture typically with a tooth, the test becoming conical 



in higher forms Family 11. Valvulinidae. 



5. Test with whole body labyrinthic, large, flattened or cylindrical. 



Family 14. Neusinidae. 



