Can anyone help me with an ID that I thought would be a cinch, but has
me baffled:
I collected a number of empty 'butterflied" bivalve pairs from sandy
beaches on the East Coast of Vancouver Island.
They are:
-extremely common on the beaches on which I found them
-up to about 2" long (at least the ones I found)
-they look similar to a Macoma as far as I can tell from pictures, most
like the Chalky Macoma - Macoma calcarea - oval, fairly compressed,
thin-shelled, muscle scars and pallial sinus similar to drawing in
Abbott's American Seashells, valves about the same inflatedness,
periostracum shiny brown to brownish-green, BUT
the most distinguishing thing about this shell is the strong purple
colour of the shell, especially inside, most noticeable when wet.  None
of my books mentions any purple colour in any Macoma or any other shell
that  can find for this area.  Some other things which are not
macoma-like as far as indicated in American Seashells, the pallial sinus
does not differ between valves as far as I can tell, but looks about the
same in each and there is no posterior twist to the shells that I can
tell.
I found a number of associated tiny pairs which I think are the
juveniles and they often are pale cream well-marked with purple rays.
Any help from you west-coast experts would be greatly appreciated.

Nora
Calgary, Alberta
-no longer on the beach :-(