How do I seal this coolant leak?

[bluesfella]

On the front of the 250 I6 in my truck, there's a coolant leak at the bottom of this curved piece (underneath the water neck):



It doesn't look like there's a gasket there. How do I seal this and keep it from leaking? It leaks pretty heavy right now, and the fan blows it back over the engine, so that when I stop, I get a nice puddle of oily black water. I can't park it on my driveway anymore.

Anyway, I've never seen a gasket listed for that piece, not even sure what to call it. Here's another pic for good measure:



Anybody know?