(Shell of Mystery Organism. To be referenced later)
I don't think this needs a scalebar, let's say it's unicellular in a fairly normal way.
Change of rules: Since the resident protistologists (and the arachnid taxonomist who knows way too much about protists to not be suspicious...) would get this very quickly, let's bar them until Friday noon Pacific Time. This one is too easy for a free beer, but if a sane person (ie. non-protistologist/aforementioned arachnid taxonomist) gets this, you get to be famous on my blog. I know, that's just awesome! Maybe about 5 people will know you! It's almost as good as being famous in math!
Guess if no one gets it by Saturday morning I'll put up a hint...
I heard phylodeities and clade spirits like beer offerings. Just sayin' Cheers~
29.09.09: think about unicellular organisms with tests. You may have even heard of a [rather polyphyletic] group of them. Google image search could help.