rash - please help

Looks more like he got burned ON something -- some pipe that got hot?  an exhaust to something?  Or could he have laid on something that had chemicals on it??

Ringworm is a different 'color' and usually on dogs the 'ring' doexn't even show.  They just lose hair inside of the ring.usually.  Now, if the hair on this falls out *inside* the ring?  Then you'll have to think ringworm again.  But that really looks like a burn of some sort. 

Stupid question -- but did you wipe it with a wet cloth -- to make sure it's not just dye from something?  Is it sore?

Another thot -- is the center swollen?  Another thot would be a bite of some sort - like a spider bite (they can do the darnedest things)

Well, vet says it's a bite - a spider mite he believes.  So the course of action is an cortisone/antibacterial ointment and oral tablets 2x a day.  Thank goodness it isn't serious - it looked awfully scary when I noticed it the other day!  The color has lightened up a lot too.