The Canon FA-DC58C is an adapter that fits the bayonet fitting on the end of the G1X lens. It is threaded to accept 58mm filter thread accessories. This means it will accept standard 58mm filters as well as accessories such as the 250D close-up lens as shown below.
The Canon LH-DC70 is a lens hood. It is a nice looking lens hood that mounts directly onto the G1X lens; unfortunately it is not threaded for filters. This means that the LH-DC70 cannot be added to the FA-DC58C filter adapter (above) and also that filters cannot be added to the LH-DC70.
I really like the looks of the G1X with the lens hood but the inability to add filters is a great business opportunity for someone – probably Lensmate.