Princess Conch or Whelk?

[cjf]

Hi all, I am relatively new to the hobby (I set up an Evo 13.5 gallon saltwater tank in April that is doing well and just set up a 55 gallon tank a few weeks ago). In any event, a few weeks ago I went to a local fish store to pick up equipment for my new 55 gallon tank and decided to purchase some Nassarius snails to help stir up the sand bed in my 13.5 gallon tank. The person at the store suggested a "princess conch" as a great addition to my clean up crew and I purchased the "princess conch" in addition to a few Nassarius snails. Anyway, over the last couple of weeks I have found the "conch" attached to a couple of now empty Astrea snail shells and I am pretty sure I saw it eating a dead hermit crab. So anyway, I would like to see if anybody here can tell me whether this thing is eating my snails/hermit crabs or if it is just a coincidence that I keep finding it in compromising positions with other members of my clean up crew. I did try to do a little research on "princess conchs" and the only other thread that popped up was this one: https://www.reef2reef.com/threads/what-the-heck-princess-snail-red-trochus-snail.470760/ and I can't tell if it is the same thing.

Here are the best pictures I could get of the thing this morning:

 

[davidcalgary29]

From what I can see from the shell, it looks like you have some species of murex, which is a carnivorous mollusc. It certainly doesn't look like a conch, which have knobby crowns and smooth lower cones. I've also never heard of a "princess" conch; Queen Conchs can grow to massive proportions and are not suitable for anything less than a massive tank.