335 



Fig. 153. a, Difflugia oblonga, Xl30 (Cash); b, D. urceolata, Xl30 

 (Leidy); c, d, D. arcula, Xl70 (Leidy); e, D. lohostoma, Xl30 (Leidy); 

 f, D. constricta, X200 (Cash); g, Centropyxis aculeata, X200 (Cash); 

 h, Campuscus cornutus, Xl70 (Leidy); i, Cucurhitella mespiliformis, 

 X200 (Wailes). 



verted; test composed of quartz grains; colorless to brown; cyto- 

 plasm colorless; 80-340// long; in the ooze of ponds and in soil. 



D. corona Wallich. Test ovoid to spheroid, circular in cross- 

 section; crown broadly rounded, with a variable number of spines, 

 aperture more or less convex in profile, central and its border 

 multidentate or multilobate; test with fine sand-grains, opaque; 

 cytoplasm colorless; pseudopodia numerous, long, branching or 

 bifurcating; 180-230^ by about ISO^t; in fresh water. 



Genus Centropyxis Stein. Test circular, ovoid, or discoid; aper- 

 ture eccentric, circular or ovoidal, often with a lobate border; 

 with or without spines; cytoplasm colorless; pseudopodia digi- 

 tate; fresh water. 



C. aculeata S. (Fig. 153, g). Test variable in contour and size; 

 with 4-6 spines; opaque or semitransparent; with fine sand-grains 

 or diatom shells; pseudopodia sometimes knotted or branching; 

 when encysted, the body assumes a spherical form in wider part 

 of test; granulated, colorless or with green globules; diameter 100 

 -150/i; aperture 50-60ju in diameter. 



Genus Campascus Leidy. Test retort-shaped with curved neck, 



