128 



COMMUNITIES OF SMALL LAKES 



Characters of the formation: The formation is distinctly dependent 

 upon a clean bottom of sand or coarser materials, and is made up of 

 creeping forms and those using the bottom as a breeding-place. 



REPRESENTATIVE ANIMALS OF THE SUBMERGED VEGETATION 



FIG. 75. Upper fish, the green sunfish (Lepomis cyanellus) ; lower fish, the yellow 

 perch (Perca flavescens) ; both juvenile; slightly reduced (original). 



FIG. 76. A viviparous snail (Vimpara contectoides); natural size. 



FIG. 77. A winter body or statoblast, of the gelatin-secreting polyzoan (Pectina- 

 tella magnified); 10 times natural size (original). 



FIG. 78. A shrimp (Palaemonetes paludosus) ; twice natural size (original) . 



b) Submerged vegetation association of the open waters. A lake of the 

 coastal type is separated rapidly from the larger body of water in con- 

 nection with which it is formed, or a morainic lake, when the ice retreats, 



