Hi,
First of all, I forgot to mention in my prior post that my BS is not green. Green BSs have a reputation for killing things are are generally regarded as predators. Non-green BSs, from I understand are generally scavengers with a tendency towards predation when starved. Ultimately, situations will vary with individual stars and avaliable food.
rfoote- "I'm wondering if I've been blaming my crabs for this and it has possibly been my brittle star."
Again, individuals will vary. But if it's a well fed, non-green, I would accept the possibility, but not expect problems. If it's a green one, then yes, I would expect it to attack and kill anything it can eat when the mood strikes. Which may be regularly or it may be never. Irregardless, I would keep on blaming the crabs.
"Simple - What do you consider as snail eating snails?"
There are a bunch. But engina and muricid are good for starters.
Here are some pictures of some engina shells. http://www.gastropods.com/Taxon_pages/Group_Engina.html You'll probably recognize the striped engina.
Members of the engina species are primarily predatory carnivores that survive on carrion if necessary. Engina snails are also buccinid snails. One of the distinguishing charactaristics of the buccinidae family is that they are equiped with a long proboscis that can rip the flesh from worms, snails, clams, etc.
There are probably about 10k different species of muricid that typcially are not sold. They are however sometimes introduced on live rock. Muricids can be particularly vicious. They have a boring organ that literally drills holes in the shells of snails, clams, worms, etc. to get the soft juicy meat inside.
Here's a page about some predatory snails. I think the conus striatus are particularly cool: http://www.animalnetwork.com/fish2/aqfm/1998/oct/wb/default.asp
mdawson8931- "I dont have anything that preys on them."
Haven't you ever seen them attack each other?
:D