C. edule or C. glaucum?

[Emma]

Hello!

Here are some photos of two Cerastoderma collected in two different places.

First one: Cornwall, Great Britain, late 1980's, dead collected by myself on a sandy beach. It is 47mm long. My guess is, it is C. edule. Do you agree? I have taken shots from different angles:








Second one: Trabucador beach, Ebro Delta, Tarragona, Spain. Collected in shallow water, off sand bottom, dead collected by myself, on Saturday, 13th of August 2011. My guess it is C. glaucum. What do you think? It is 36 mm.







Please let me know what you think, and if you could help with classifying the Unknown conus, 3 posts before this one, thank you.

Best wishes,

Emma.

[paul monfils]

The first one is certainly C. edule.  I would say the second one, based on external appearance (less flattened ribs with wider spaces between), is most likely C. glaucum.  However there is one typical characteristic of C. glaucum that I don't see on your specimen.  Because the shell is usually quite a bit thinner than that of C. edule, you can usually see the lines of the ribs on the interior of the shell, from the lip all the way to the umbones, while in C. edule you can only see them in a narrow band near the lip.  But in spite of that variation, I would go with C. glaucum.

[Emma]

Thanks Paul!!

I had a look on a Natural history web page: <!-- m --><a class="postlink" href="http://www.nmr-pics.nl/Cardiidae/album/">http://www.nmr-pics.nl/Cardiidae/album/</a><!-- m -->, and on that page it looks like C. glaucum, but a friend who I went shelling with said that C. glaucum couldn't be found in that area of the Mediterranean.
However, on previous trips, and by consulting the book on Ebro specimens by Brunet I have always come up with the same solution: C. glaucum.

Thanks again!

Best wishes,

Emma.

[dave r]

Although it does resemble glaucum superficially I would still have my doubts. Glaucum,as mentioned above, is always a lighter, thinner shell and the ribbing does go up to the umbones in glaucum. Glaucum is also a shell of lower salinities preferring more brackish waters than edule, you mentioned your specimen was from the Ebro delta, was it in brackish waters or in the open sea?

[Emma]

Hello Dave,

Could it be Cardium pauciostracum? This was the name of the specimens they had in the Ecomuseum on the Delta. I collected them in shallow sea water, because the tide was out, on sand. They were deffinetely sea specimens because some of them had sea weed, and last year a Hexaplex trunculus had one of these shells in its grip.

Best wishes,

Emma.

[dave r]

Hi Emma
I don't know where they got the name 'pauciostracum' from but I can find no trace of it. The nearest I can find is Acanthocardia paucicostata but the shell you illustrate is definitely not this species. I would still say a form of edule myself.

[Emma]

Ok, thanks Dave!

Emma.