COMMUNITIES 39 



purely physiological points of view. Accordingly some communities are 

 mentioned more than once. Others have two names. 



I. Stream Communities 



1. Intermittent stream communities 



a) Intermittent rapids consocies 



b) Intermittent pool consocies 



c) Permanent pool, or horned dace association 



2. Permanent stream communities 

 a) Spring dominated stages 



1) Spring consocies 



2) Spring brook associations 



3. Creek and river communities 



a) Pelagic sub-formation 



b) Hydropsyche, or rapids formation (turbulent-water formations) 



c) Anodontoides ferussacianus, or sand or gravel-bottom formations 



d) Sandy-bottomed stream sub-formation (shifting-bottom sub- 

 formations) 



e) Silt or sluggish-stream communities 



1) Sluggish-creek sub-formations 



2) Pelagic formations 



3) Hexagenia, or silt-bottom formation 



4) Planorbis bicarinatus, or vegetation formation 



II. Large Lake Communities 



1. Pelagic formations 



2. Eroding rocky-shore sub-formations (turbulent- water formations) 



3. Depositing sandy-shore sub-formations (shifting-bottom sub-forma- 

 tions) 



4. Lower-shore formations 



5. Deep-water formations 



III. Lake-Pond Communities 



1. Pelagic sub-formations 



2. Pleurocera subulare, or terrigenous-bottom formation 



3. Vegetation formation 



a) Leptocerinae, or submerged vegetation association 



b) Neuronia, or emerging vegetation association 



4. Temporary pond formations 



IV. Prairie or Grassland Formation of the Savanna Climate 



1. Xiphidium fasciatum, or grassland association of moist ground and 

 marsh vegetation in the savanna and forest climates 



2. Prairie chicken, or high-prairie association of the savanna climate 



