A-1.— List of species and area of occurrence (Continued) 



* * Considered a synonym for S. alta by Grant and Gale (1931). 



"Apparently the only differences between Siliqua media and S. patula are that the rib on the inside is more nearly vertical in 

 S. media, and S. media is heavier than S. patula. Future study may show that these differences are invalid for there may be inter- 

 grades as far as the ribs are concerned. And the heaviness or thickness of the shell is a common characteristic of Arctic shells 

 and is not a reliable dia^ostic characteristic." (N. MacGinitie, personal correspondence). 



Considered by Grant and Gale (1931) as a variety of Mya arenaria (Linnoeus). 



28 



