Has an elongated shell. Hairy on the outside. First emerged out of the sand after about 2 months setting up the tank. Stays very still. Does open and close. Has moved slightly. Picture shows it next to a small hermit shell.
Still working on getting a better pic (more due to lack of a good camera than anything). He has shifted positions a few times. But this thing is definitely not mobile. Opens up like a clam shell and is filter feeding. But not the shape of a clam, more elongated.