I got a frag of zoas from a club member recently and found some pods I was worried about. It turns out they are perfectly safe, and called Sand Skaters. I posted about these a month ago, but here's the answer I got from Dr Ron today.
http://forum.marinedepot.com/Topic71834-11-1.aspx?Update=1
http://forum.marinedepot.com/Topic71834-11-1.aspx?Update=1