TESTACEA 329 



lated and usually evarted within inverted funnel; protoplasmic 

 body spheroidal, with 'neck' to aperture and cytoplasmic strands 

 to test; 6 or more slender lobopodia; test 100-145)U high, 100- 

 152/i in diameter; in fresh water among vegetation. 



A. catinus Penard (Fig. 150, e, /). Test oval or quadrate, not 

 circular, in front view; aperture oval; dome compressed; lateral 

 margins with 6 or 8 facets; test 100-120/i in diameter and about 

 45^1 high; fresh water among vegetation. 



A. dentata Ehrenberg (Fig. 150, g-4). Test circular and dentate 

 in front view, crown-like in profile; diameter more than twice the 

 height; aperture circular, large; colorless to brown; about 95/i 

 in diameter, aperture 30/x in diameter; 15-17 spines; in the ooze 

 of freshwater ponds. 



A. artocrea Leidy (Fig. 150, j, k). Height of test 1/4-1/2 the 

 diameter; dome convex; surface mamillated or pitted; border of 

 test everted and rising 1/4-1/2 the height of test; about 175/x in 

 diameter; fresh water. 



Genus Pyxidicula Ehrenberg. Test patelliform; rigid, transpar- 

 ent, punctate; aperture circular, almost the entire diameter of 

 test; cytoplasm similar to that of Arcella; a single nucleus; 1 or 

 more contractile vacuoles; fresh water. 



P. operculata (Agardh) (Fig. 151, a, h). Test smooth, colorless 

 to brown; a single vesicular nucleus; pseudopodia short, lobose 

 or digitate; 20^ in diameter; on vegetation. 



Genus Pseudochlamys Claparede et Lachmann. Test discoid, 

 flexible when young; body with a central nucleus and several 

 contractile vacuoles. 



P. patella C. et L. (Fig. 151, c). Young test hyahne, older one 

 rigid and brown; often rolled up like a scroll; a short finger-like 

 pseudopodium between folds; 40-45)U in diameter; in fresh water 

 among vegetation, in moss and soil. 



Genus Difflugiella Cash. Test ovoid, not compressed, flexible 

 and transparent membrane; colorless cytoplasm fills the test, 

 usually with chlorophyllous food material; median pseudopodia 

 lobate or digitate with aciculate ends, while lateral pseudopods 

 long, straight, and fine, tapering to a point; fresh water. One 

 species. 



D. apiculata C. (Fig. 151, d, e). About 40^ by 28/^; among vege- 

 tation. 



Genus Cryptodifflugia Penard. Small test yellowish to brown- 



