^^^.p^r■^ 





Figure 9 — PJu/sa habitat at Crooked Lake formed behind s]iit. Optimum near 



the center of the picture. 





■■.^::"-: 







FiGi;i;i: 10 — Lymnaea palu.-,ui>, .-^eak-d iii clay. .Swamp C. Daylon, Tuscola County 



Michigan. 



