PLATE XXX. 



Figs. l-'J.— AECELLA ARTOCREA. 200 diameters. 



Figs. 1,2. Inferior and lateral views; the former exhibiting the interior sarcode with its abun- 

 dance of chlorophyl grains. Absecom pond. New Jersey, September, 1874. 



Figs. 3, 4. Inferior and lateral views of a shell. Sphagnum of Absecom, N. J., April, 1876. 



Figs. 5, 6. Inferior and lateral views of a shell ; in the former with irregularly oval outline. 

 Found with the preceding. 



Figs. 7, 8. Inferior and lateral views of an individual, with the sarcode in an encysted condition. 

 Shell with an irregularly oval outline as seen in the former view. The ball of sarcode produced an 

 eversion of the base of the shell as seen in the lateral view. In the interval of the sarcode and shell a 

 number of amoeboid corpuscles were visible. With the preceding. 



Fig. 9. Lateral view of a large empty shell. Absecom pond, N. J., September, 1874. 



Figs. 10-19.— ARCELLA DENTATA. 250 diameters. 



Figs. 10, 11. Inferior and lateral views of an empty shell. Ditch below Philadelphia. 



Figs. 12, 13. Inferior and lateral views of a shell. Fairmount, Philadelphia. 



Figs. 14, 15. Upper and lateral views of a shell. Budd's Lake, New Jersey, October, 1874. 



Figs. 16. 17. Inferior and lateral views of a shell. Ditch below Philadelphia. 



Fig. 18. Lateral view of a shell. Budd's Lake, New Jersey. 



Fig. 19. Inferior view of a living individual. The sarcode exhibits a pair of opposite nuclei, 

 several contractile vesicles, and a projected pseudopod. Found with the preceding, a, nucleus; ft, 

 contractile vesicle. 



Figs. 20-34.— CENTEOPYXIS ECORIHS = the > spineless variety of CENTROPYXIS ACULEATA. 



I he shell in most examples composed of sand grains, cemented in close juxtaposition. 200 

 diameters. 



Fig. 20. Inferior view of a living individual, with protruded pseudopods. The shell with large 

 sinuous mouth ; the height about one-third the breadth. Ditch below Philadelphia, September, 1875. 



Figs. 21,22. — Inferior «nd lateral views of an empty shell. Swarthmore brick-pond, Delaware 

 County, Pa. 



Figs. 23, 24. Inferior and lateral views of an empty shell, with a large circular mouth. Fairmount 

 Park, Philadelphia. 



Fig. 25. Inferior view of a shell, with a small circular mouth. Ditch below Philadelphia. 



Fig. 26. Inferior view of a shell, with trilobed mouth. Pond on Darby Creek, Delaware County, 

 Pennsylvania. 



Fig. 27. Inferior view of a shell, with quadrilobed mouth. Same locality. 



Figs. 28, 29. Inferior and lateral views of a shell, with quadrilobate mouth. China Lake, Uinta 

 Mountains, Wyoming. 



Figs. 30,31. Inferior and lateral views of a living individual, with extended pseudopods. The 

 brown shell, composed of sand grains, with the cement of a darker hue of the same color. Ditch below 

 Philadelphia, June, 1874. 



Fig. 32. Inferior view of a living individual, with extended pseudopods. The shell composed of 

 chitinoid membrane incorporated with dirt and sand. Pond on Darby Creek, Delaware County, Pa., 

 October, 1874. 



Figs. 33, 34. Inferior and lateral views of an empty shell, composed of sand. Same locality as the 

 preceding. 



