M. 



LISTS OF FEESH- WATER EIIIZOPODS. 291 



34. Hyalolampe fenestrata. All rayless individuals. Occasional. 



35. Acanthocystis ? With delicate, simple, unforked spines. Occasional. 



36. Amphizonella violacea ? A single individual; l'or the first time observed. In 



the spheroidal form about 0.15 mm. diameter ; endosarc of a deep violet hue ; 

 ectosarc colorless. Animal remained nearly stationary in position, with slight 

 changes of form, and emitted from one to three digitate pseudopods, sometimes 

 blunt, sometimes pointed, even or irregular, clear and colorless at the periphery 

 and ends, but violet internally at the base. 



37. Amceba radiosa. Occasional. 



38. A. peoteus "? Occasional. 



With the Rhizopods there were associated a multitude of desmids — 

 MicrasteriaSj Euastrum, Doeidium, Closterium, etc , diatoms, etc., etc. 



II. EHIZOPODS OBSERVED IN MATERIALS COLLECTED IN THE TRAP 

 REGION OF ROCK HILL, BUCKS COUNTY, PENNSYLVANIA, JUNE 



27, 1879. 



a. From sediment of a ditch traversing a meadow in which grew 

 Spatter-dock, Nupliar aclvcna. 



1. Difflugia globulosa. Ovoid variety, with the narrower pole truncated by the 



circular mouth, which sometimes has a short, straight, or a slightly everted rim. 

 Shell composed of fine quartz-sand or of chitinoid membrane incorporated with 

 thin angular plates of quartz. Endosarc colorless. Length 0.09 mm. ; breadth 

 0.06 mm. ; width of mouth 0.024 mm. Frequent. 



2. D. PYRrromiis. Ordinary forms, mostly small. Shell of quartz-sand. Endosarc 



in some green, in others colorless. Frequent. 



3. D. acuminata. Shell of chitinoid membrane incorporated with variable propor- 



tions of thin angular plates of quartz-sand. Few. 



4. D. lobostoma. Shell nearly spherical or oval, composed of angidar quartz-sand ; 



mouth trilobate, sometimes with a short and slightly reflected rim. Endosarc 

 green. Frequent. Variety with smoky-colored shell, composed of fine angular 

 sand, in shape spheroidal, oval or ovoid, and even, or mammillary, like D. tuber- 

 culata, Wallich; mouth six-lobed, with or without a narrow projecting rim. 

 Length 0.132 mm. ; breadth 0.12 mm. ; width of mouth 0.036 mm. Frequent. 

 Variety with shell of chitinoid membrane incorporated with variable proportions 

 of thin angular plates of quartz ; endosarc colorless. Few. 



5. D. consteicta. Of varied sizes and proportions ; yellow and colorless shells of 



quartz-sand. Frequent. 



6. D. spiralis. Characteristic specimens with shell of quartz-sand. Occasional. 



7. Centropyxis ACULEAta. Abundant, of considerable variety, large and small, 



mostly yellow or brown, and generally having the chitinoid shell incorporated 

 with much sand. Variety C. ecornis. Frequent and merging into Difflugia con- 

 stricta. 



8. Arcella vulgaris. Shell with even, convex, and with mammillated or cupped 



fundus. Frequent. 



