Blew something

I hooked up my VIN and GND pins up to a 8v power source and blew what looks to be a capacitor (or fuse) labeled 47-16L WD 2, it is located near the standardized power connector. This is on the mega btw. Anyone have any insight to what it is and how to get a replacement?

Is it the black thing, if so it is a diode. However before you go replacing things you have to find out what you did wrong in the first place. Things to check. 1) Is the polarity of your PSU what you think it is. (a blown diode would suggest not) 2) Is your PSU DC, it could be you have an AC one (that would blow up a capacitor)