TESTACEA 



477 



meter; in the ooze and vegetation in stagnant water and also in soil. 

 Of several varieties, two may be mentioned; var. angulosa (Perty), 

 test smaller, 30-40/i in diameter, faceted, forming a 5- to 8-sided 

 figure, with obtuse angles; var. gibbosa (Penard), test gibbous, sur- 

 face pitted with circular depressions of uniform dimensions: 45-50xi 

 up to 100/z in diameter. 



x^cSW 



Fig. 201. a, b, Arcella vulgaris, X170; X230 (Leidy); c, A. discoides, 

 X170 (Leidy); d, A. mitrata, X140 (Leidy); e, f, A. catinus. X 170 (Cash); 

 g-i, A. dentata, X170 (Leidy); j, k, A. artocrea, X170 (Leidy). 



A. discoides E. (Fig. 201, c). Test circular in front view, plano- 

 convex in profile; diameter about 3-4 times the height; test color- 

 ation and body structure similar to those of A. vulgaris; test 70- 

 260/t in diameter; in fresh water. 



A. mitrata Leidy (Fig. 201, d). Test balloon-shaped or polyhedral; 

 height exceeds diameter of base; aperture circular, crenulated and 

 usually evarted within inverted funnel; protoplasmic body sphe- 

 roidal, with 'neck' to aperture and cytoplasmic strands to test; 6 or 

 more slender lobopodia; test 100-145/* high, 100-152/* in diameter; 

 in fresh water among vegetation. 



A. catinus Penard (Fig. 201, e, /). Test oval or quadrate, not 

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

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

 45/i high; fresh water among vegetation. 



A. dentata Ehrenberg (Fig. 201, g-i). Test circular and dentate 



