456 



MARINE INVERTEBRATES 



FAMILY MYIDJE 



GENUS Mya 



In this family we encounter, rather suddenly, some new fea- 

 tures not heretofore seen in the pelecypod structure. In the 

 first place, the siphons are enormously large, are united, and are 

 surrounded by a leathery epidermis. The mantle-edges are fused 

 together along the entire ventral margin, except for a small slit 

 through which the foot may project. Although the animal may 

 withdraw the long siphons into its shell, yet they remain to a 

 certain extent exposed, for the valves gape widely posteriorly, 

 and only slightly less so anteriorly. In the economy of these 

 forms the shell seems to play a less important part than it does 

 in the Veneridce, in the Tettinidce, and generally in those families 

 whose shells are strong and, closing firmly, afford the animal 

 within a real protection. The shell of Mya (the principal genus) 

 is thin, white, and of a softer chalky texture ; it gapes widely 

 "fore and aft," and has a loosely constructed hinge apparatus, 

 consisting of an erect projecting tooth, which fits into a pit in 

 the opposite valve. 



M. arenaria. This is the common "soft-shell clam" of New Eng- 

 land. Its range is from Cape Cod to Greenland and Great Britain. 

 Upon the Maine coast it is very extensively gathered and sold to the Banks 

 fishermen for bait. Its use as food for man is probably not very great, 

 yet it is always to be seen on sale in the markets of New England coast 

 towns. It cannot compare in flavor with Venus wercenaria, the " hard- 

 shell clam" south of Cape Cod. M. arenaria lives between tides in 



muddy, sandy, peb- 

 bly, or even rocky 

 ground, where it 

 can find material in 

 which it can burrow 

 and hide itself. It 

 lies just below the 

 surface, with its si- 

 phons projected into 

 the water. When 

 the water recedes, 

 Mya draws in its si- 

 phons and awaits the 

 return of the tide, 

 every now and then 



