Mark - not a cross

[miw]

Hi,
I have a parish register entry from 1828 where the bride has made her mark not as a cross but as a circle containing a dot.  I don't remember ever seeing this before, we have all seen many variations of the cross both + and x and I think I have seen it with a dot in each quarter.  Does anyone know of any particular significance of this mark.

I would be interested in any thoughts on this.