Hi,Well I think googling has provided me with the info I need so I figured I'd post it up here in the interests of making the information more accessible
The diagram below supposedly indicates a female, they have an extra structure (tooth as its been referred to, but its quite seperate from the other pectinal teeth) on the pectines. The arrow points to that structure which I believe only females have:
http://img211.imageshack.us/i/parasxingcd2.jpg/