TESTACEA 341 



oblique, invaginate; nucleus posterior; filopodia not branched; 

 fresh water in vegetation. 



T. enchelys (Ehrenberg) (Fig. 156, a). 1-2 contractile vacuoles; 

 pseudopodia attenuate, radiating; 30-1 00/x long; 15-60/i wide; 

 scales 4-12^1 in diameter. 



Genus Corythion Taranek. Test small, hyaline, composed of 

 small oval siliceous plates; compressed; elliptical in cross-section; 

 aperture subterminal, ventral or oblique, and circular or oval; 

 numerous filopodia; fresh water. 



C. pulchellum Penard (Fig. 155, e,f). Aperture lenticular; cyto- 

 plasm colorless; 2-3 contractile vacuoles; 25-35/^ by 15-20^i; 

 aperture 7-10^1 by 3-4/x. 



Genus Placocista Leidy. Test ovoid, hyaline, compressed; len- 

 ticular in cross-section; with oval or subcircular siliceous scales; 

 aperture wide, linear, with flexible undulate borders; nucleus 

 large, posterior; often with zoochlorellae; filopodia branching and 

 many, generally arising from a protruded portion of cytoplasm; 

 fresh water. 



P. spinosa (Carter) (Fig. 156, 6). Margin of test with spines, 

 either singly or in pairs; 116-174^t by 70-100ai; in sphagnum. 



Genus Assulina Ehrenberg. Test colorless or brown; ovoid; 

 with elliptical scales, arranged in diagonal rows; aperture oval, 

 terminal, bordered by a thin chitinous dentate membrane; nu- 

 cleus posterior; contractile vacuoles; filopodia divergent, some- 

 times branching; fresh water. 



A. seminulum (E.) (Fig. 156, c). Body does not fill the test; 

 with numerous food particles; pseudopodia few, straight, di- 

 vergent, slender, seldom branched; 60-1 50/x by 50-75ju; in sphag- 

 num. 



Genus Nebela Leidy. Test thin, ovate or pyriform; with cir- 

 cular or oval platelets of uniform or various sizes; highly irregu- 

 lar; endoplasm with oil-globules; nucleus posterior; body does 

 not fill the test, and is connected with the latter by many ecto- 

 plasmic strands at fundus end; pseudopodia blunt, rarely 

 branched; fresh water. Numerous species. 



N. collaris (Ehrenberg) (Fig. 156, d). Test pyriform, fundus 

 obtuse in profile; aperture without any notch; endoplasm wdth 

 chlorophyllous food particles; pseudopodia digitate, short, usu- 

 ally 3-6 in number; about 130^1 by 85-90/i; in marshes among 

 sphagnum. 



