Well, I'm a bit flabbergasted at what I found out today...
I thought it a bit odd that I had never seen a
squamosa clam with coloration like mine, and while browsing clamsdirect earlier this evening, I found a clam that looks exactly like mine... a T. deresa...

Well, I guess I can claim ignorance, being that I in fact ordered a T. squamosa from liveaquaria... and that is what I should have gotten.
Of course, I discover this long after the 10-day guarantee is up...

I think they need to teach their packers at liveaquaria the differences between species... they shipped me a hammer coral instead of the
green frogspawn I had ordered (which they made good on, but sent me a 'yellow' frogspawn instead of green), and now I discover they sent me a T. deresa...
Well, at least their customer service is top notch...

So I guess I stand corrected on my first pic (the one that started this thread)... it is a nice clam though it isn't what I thought it was.
