white circle in my yeast starter?

[batty]

Just started this thing yesterday, seemed like it had finished already and the yeast had dropped out (it got pretty cool). randomly today this white circle appeared on the surface, seemed like it was increasing (getting thicker) as the day went on. Any thoughts on if this is ok to use? Smells fine, but don't want to put any nasties in my beer! thanks,

 

[jasonsbeer]

picture?

 

[Revvy]

Krausen beginning to form, or at least yeast rafts. Perfectly normal