i84 A NATUILILIST IN THE GREAT LAKES REGION 



family Sphaeridae (Fig. 2q8) . One thinks on first sight that these 



are the young of the larger clams, 

 but such disappear from the dune 

 ponds with the replacement of the 

 sandy bottom by the muddy bottom. 

 In the Sphaeridae the lateral teeth 

 of the shell are found on both sides 

 of the cardinal teeth, while in the 

 larger clams they occur on one side 



Fig. 207 Fig. 208 



Figs. 207, 208: Fig. 207. — Shrubby cinqxieh'A, Polenlilla friiticosa; Fig. 208. 

 A small clam, Sphacriiini simile. 



Fig. 209. — Molt skin, nymph of Anax 



only. A few mud-loving fish are present, like the black bullhead, 

 similar to the spotted (Fig. 193) but dark brownish or greenish 



