Lamp fixture seems too hot?

I have a 100w night light for my new veiled chameleon and it's screwed into a light fixture that says 250V 660W on it. I assume that means the max bulb it will accept is 660W. is this correct? my 100w night bulb seems to be extremely hot to the point that the bulbs metal screw threads are changing color and it almost looks like the side connection is melted