Looks kinda like a trumpet shell. Check out this thread:

http://www.reefcentral.com/vbulletin...=trumpet+shell

Looks like the photos are no longer available but could just be my comp...

I have the same type of snail. They are deffinately predetory. They do not eat algae according to Dr Ron. I don't remember what he called them though. The problem I had with them was that they multyiplied so fast that they were overtaking my tank. I thought I had gotten all of them, but I just noticed that a new batch of babies has sprouted up. Back to getting me hands wet.