There's a folder shortcut on my dock, next to the trash. Why is there and how do I remove it? I want my dock to be purely for shortcuts to the programs I use the most. Frankly it annoys me that you can't remove the Trash from the dock, but I can live with that. 

What I really want to get rid of is this folder shortcut that I have next to the Trash. I think it's called a stack? It's to the right of the dividing line that separates my application shortcuts from the trash icon. When I right-click it, there's no option to remove it from the dock.

My question is two-fold- 


Why do I have this shortcut there to that specific directory?
How do I get rid of it?


I'm very new to OSX, so forgive me if I'm missing something obvious here.

Edit: Screenshot of what I see when I try to remove it:



Edit2: I'm on Mountain Lion, 10.8.1.

Edit3: I should mention that the folder in question is not on my local machine. It's a networked drive, mounted at /Volumes/Student/Home/6514944/.
Simply click on it to hold it then drag it off of the dock and release the click. It should disappear in an animated puff of smoke.