PLATE XV. 



FIGS. 



1-3. Arcella vulgaris Ehrenb. (p. 118) Pond, Cheshire, 

 x 300. Fig. 1. A young individual, in active 

 movement, with transparent test. Figs. 2 and 3. 

 Empty tests of the same form. 



4-6. A. discoides Ehrenb. (p. 122) Pond, Cheshire, x 300. 



Figs 4 and 5. Lateral and dorsal views of living 



individuals. Fig. 6. A young individual with 



imperfectly-formed test. 



7, 8. A. dentata Ehrenb. (p. 125) Dorsal and lateral 



views, showing character of test. x 300. 

 9,10. A. mitrata Leidy. (p. 124) Dorsal and lateral views, 

 after Leidy. x about 300. 



11, 17. A. vulgaris var.gibbosa (Penard) G. S. West. (p. 121) 



A small variety, with facetted test. Frequent in 

 ponds, x 300. 



12, 16. A. vulgaris var. angulosa (Perty) Leidy. (p. 121) In 



outline, after Leidy. x 250. 



13-15. A, vulgaris. Figs. 13 and 14. Dorsal and lateral 

 views of a young individual ; the test transparent, 

 with dilated base. Fig. 15. A remarkably fine 

 variety, with pitted test. Pond at Park Bridge, 

 Lancashire. x 300. 



