Well, maybe I'm wrong.
But the pattern is one I've seen on pictures before for maximas. Maybe I'm overlooking something, but my first thought was "Wow what a nice maxima! But why didn't he post a picture of the squamosa!" Maybe I should have looked closer at the shell. Squamosa scutes are so noticeably more exaggerated and further apart from one another than those on maximas or croceas.
But ultimately, whatever it is: it is one wickedly pretty clam. I want one too!
It was VERY hard making a decision the other day. I could have easily picked 4 right off the bat.