11/30/10: I posted on Conch-L:

"We don’t have M. edulis in live populations in Florida, but I did come across some beach shells on a recent trip to Wallops Island, Virginia. Maybe some of our members in the more northern climes may wish to share comments or photos."

Comments received:

Harry Lee:

"As regards its occurrence in FL, Bill Hanson, a Jax Shell Club member of yore, actually found living Mytilus edulis attached to driftwood stranded on Jacksonville Beach in October, 1986. It has been considered doubtful that this species would survive the warmer months (Lee, 2009: 18) here. Indeed, subsequent finds in our appear to derive from anthropogenic "middens."

Your text indicates you may have overlooked the anterior adductor muscle scar." (Note: oversight corrected in above slides.) "The shape and location of the scars marking the attachment of the anterior (absent in four of the two dozen plus genera) adductor, posterior adductor, anterior byssal retractor, and posterior byssal muscles are crucial to the higher taxonomy of the Mytilidae, or true mussels (Soot-Ryen, 1955).

Lee, H.G., 2009. Marine shells of northeast Florida. Jacksonville Shell Club, Jacksonville, FL. Pp. 204 + 19 color pls. 28 May.

Soot-Ryen, T., 1955. A report on the family Mytilidae (Pelecypoda). Allan Hancock Expeditions 20(1): 1-174 (incl. 78 text figs) + 10 pls. Nov. 10."

Steve Rosenthal:

"Shells typically are all blue, or various shades of brown- eg grayish brown (as illustrated by you). I have some that are very light golden brown/olive brown. Also lots of darker brown shells that range to dark chestnut brown, often you see brown shells with blue/black rays, I am aware of one albinistic ("dirty white") shell from Bar Harbor, Maine. I have not seen this shell or an image, but it is from a reliable source. I have seen images of lighter blue shells with darker bluer rays but they may have been brought out by post-mortem wear/fading, bleaching, or excessive cleaning/removal or loss of periostracum.

Regarding size I have specimens up to 112mm (also from Bar Harbor Maine). Markus Huber told me that the WRS is something around. 125mm, if I recall correctly.

Regarding habitat, though most books typically note the rocky substratum, I see many dense populations of thickly matted individuals on mudflats (eg Shinnecock Bay in NY; the west side of the bar at Bar Harbor, which is where all my 100mm+ shells came from), so obviously the species can be successful in different habitat types."