292 FRESHWATER RHIZOPODS OF NORTH AMERICA. 



9. Arcella. One specimen observed with transversely oval shell 0.1 mm. long, 

 0.072 mm. broad, and 0.036 mm. high, with mouth 0.045 mm. in the long and 

 0.024 mm. in the short diameter. Even convex fundus and of bright burnt- 

 sienna color. Animal active. 



10. Nebela collaris. Narrow form with the cancellated structure of the shell 



obscurely developed. Rare. 



11. Trinema enchelys. Abundant, and of varied size and development. 



12. Cyphoderia ampulla. Well developed and active ; shells yellowish and color- 



less. Frequent. 



13. Euglypha alveolata. Small spineless forms, of variable sizes and proportions, 



and with 4, 6, and 8 teeth to the mouth. Frequent. 



14. Eugltpha ciliata. With and without lateral hairs. 



15. Pseudodifflugia gracilis. Oval form. Occasional. 



b. Contiguous to the ditch, from which the former were obtained, in 

 the same meadow, there grew an unusual profusion of Selaginella apus. Por- 

 tions of the plant, with earth adherent to the roots, on being moistened and 

 squeezed, gave a sediment, which, besides many bright active diatoms, des- 

 mids, etc., yielded the following Rhizopods : 



1. Dieplugia globulosa. Shell oval or ovoid, even, colorless or yellowish, com- 



posed of chitinoid membrane incorporated with variable proportions of thin, 

 irregular, angular plates of quartz, or composed of small sand particles. Mouth 

 truncating the narrower pole, circular, sometimes with a short, straight, or 

 slightly everted rim. Endosarc colorless. Length 0.072 mm. to 0.09 mm. ; 

 breadth 0.036 mm. to 0.048 mm. ; width of mouth 0.01S mm. Frequent. 



2. D. pyrlformis. Small form ; shell of quartz-sand. Length 0.108 mm. to 0.156 



mm. Not unfrequent. 



3. D. constricta. Of varied proportions, colorless and yellowish, and merging into 



Centropyxis ecomis. Frequent. 



4. Quadrula symmetrica. Occasional. Length 0.072 mm.; breadth 0.036 mm. 



5. Arcella vulgaris. Living and active. Shell with cupped fundus. Occasional. 



6. Trinema enchelys. Abundant and of varied sizes and proportions, and with 



varied degrees of obliquity. Ranging from 0.024 mm. to 0.096 mm. in length. 

 A specimen constricted just above the position of the mouth was 0.96 mm. long, 

 0.042 mm. broad at the fundus, and 0.03 mm. wide opposite the mouth, which 

 was 0.021 mm. wide. 



7. Euglypha alveolata. Small forms, spineless, with 4, 6, and 8 teeth to the 



mouth. From 0.03 mm. to 0.72 mm. long; 0.018 mm. to 0.036 mm. broad. 

 Frequent. 



8. E. ciliata. Compressed forms, with lateral hairs, and 4- to 6-toothed. A speci- 



men observed with divergent hairs to the summit of the fundus in addition to 

 the lateral ones. Its length 0.06 mm.; breadth 0.03 mm.; mouth 0.012 mm.; 

 nucleus 0.012 mm. Occasional. 

 !). Cyphoderia ampulla. Several dead shells. 



10. Sphenoderia lenta. Common form. Occasional. Also a variety 8. dentata, 

 with oval shell, composed of oval, overlapping plates ; neck short or obsolete ; 

 mouth elliptical, oblique, with the border minutely denticulated. Length 0.054 

 mm. : breadth 0.03 mm. ; width of mouth 0.012 mm. 



