undocumented pin on arduino duemilanove ?

Development Tools IDE 1.x
1

One side of the board has the folowing pin layout

[ reset - 3v3 - 5v - ground - ? - Vin ] [analog 0 - analog 1- analog 2 - analog 3 - analog 4 - analog 5]

at around Vin, there is a pin that is not documented before or after i'm not sure so it could be
[ reset - 3v3 - 5v - ground - ? - Vin ]
or
[ reset - 3v3 - 5v - ground - Vin -? ]

So i wonder what this ? does, is it perhaps a place to attach external wires for power togther with Vin (instead of usb/or plugin conector) ?

if it is not what is it ?

and if it is not where should i connect (solder) wires to connect to an external power

2

According to the schematic (http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf), there are two ground pins.

3

it's even silk screened onto the board