360 BIOLOGY OF THE PROTOZOA 



2. Aperture of test circular 3 



Aperture of test ellipsoidal or linear Genus Plagiopyxis 



3. Aperture without lobed external collar. ... 4 

 Aperture with three or four lobed external 



collar Genus Cucurhitella 



4. Aperture excentric in position Genus Centropyxis 



Aperture central ; sjTiimetrical 5 



5. Test covered with diatom shells; pseudo- 



podia pointed Genus Phryganella 



Test covered with sand, mud, detritus, etc. 



(Fig. 155) '. Genus Difflugia • 



Fig. 155. — Difflugia lohostoma plastoganiic stages formerly interpreted as evidence 

 of conjugation. (From Calkins after Rhumbler.) 



6. Test with constricted neck and internal 



shelf. Genus Pontigulnsia 



Test without internal shelf 7 



7. Test with foreign particles on dome only. . 8 

 Test covered; aperture a long and narrow 



slit Genus Bullinula 



8. Aperture of test convex Genus Heleopera 



Aperture small, ellipsoidal, with thickened 



margins Genus Awerintzia 



Family 3. Euglyphidae. 



1. Cells without chromatophores 2 



Cells with one or two blue-green chroma- 

 tophores Genus Paulinella 



2. Test curved, retort-shape 3 



Test dome-shape; not curved 5 



