Bust of a cat

thingiverse

I was just reading the thingiverse blog old entries and found out about sculptris. So I ran it through some tests, and this is the second drawing that popped out. Surprise: it's another cat drawing. There's some weird thing going on internally with the mesh. I couldn't figure out how to fix this in meshlab or any other tool. Does anyone know how to kill internal vertices in a model?