•, 



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'.. 



^PORTLAND 











. ' . BOS 



TON 











NE\W;,& 



TORK-i-i-a 







: ATLA 

 :CITY 



; - 



NORFOLK 



Figure 99. — Geographic distribution of Siliqua coslata and Solemya borealis. Figure 100. — Geographic distribution of Solemya velum and Spisuln polymma. 



117 



