Purple-bodied Nassarius Snails?

[Spork3245]

I bought some "Nassarius Snails" from a LFS the other week, however I noticed that some of them were colored differently than my previous nassarius snails and had "creamier" colored shells as well as dark bodies (a couple of them are also very large, over an inch in length). I've only recently learned of "Babylonian Snails" which are often sold as "Fancy/Speckled Nassarius Snails" and am now worried that I unleashed a bunch of predatory snails into my tank, especially since my nassarius snail population seems to have shrunk over the past couple of weeks.

A couple of lone pictures (this is not the "giant" one I mentioned, he must be buried in the aragonite somewhere ):

A side-by-side photo with a "regular" nassarius:

I also realize I may just be overly paranoid here and that they just may be a different species of nassarius and are "good" snails, however there seems to be about 10+ snails that have gone missing since adding these newer ones (unless they're hiding out in the back where I can't see them ) and I just don't think my 3 blue legged hermits could've taken that many nassarius out while leaving all of my astrea snails alone.

Thanks!

 

[Spork3245]

Anyone? Bueller...?

 

[cloak]

If you haven't already, you might want to post these pictures in the Other Invertebrates Forum. There's a few people there who are really good at identifying things.

 

[Sugar Magnolia]

If you haven't already, you might want to post these pictures in the Other Invertebrates Forum. There's a few people there who are really good at identifying things.

Yes, PagoJoe is our resident snail guru. You could send him a PM with a link to this thread.

 

[Spork3245]

Thanks guys, reposted the thread in other inverts!
My biggest concern isn't so much having missing snails but, if these are predatory snails, having them deplete my live-sand bed leaving my Diamond Goby SOL (though he does eat frozen, flake and pellet food as well as chunks of nori and pretty much anything else that's edible that floats by him)

 

[devimik]

If what I'm seeing is a protective shell on the rear part of the foot, it's likely a predatory Whelk. They have this feature that allows them to seal themselves into their shells and Nassarius Vibex don't. Whelks are usually darker and have a more pronounced pattern on their skin as well. Also, Whelks don't spend much time under the surface of the sand like Nassarius. Here's a good link. http://www.melevsreef.com/id/whats_a_whelk.html

 

[Spork3245]

If what I'm seeing is a protective shell on the rear part of the foot, it's likely a predatory Whelk. They have this feature that allows them to seal themselves into their shells and Nassarius Vibex don't. Whelks are usually darker and have a more pronounced pattern on their skin as well. Also, Whelks don't spend much time under the surface of the sand like Nassarius. Here's a good link. http://www.melevsreef.com/id/whats_a_whelk.html

Yea, I read that about whelks (they don't stay buried like nassarius usually do) but these guys seem to only "emerge" from the substrate at feeding times like the others and also do bury themselves and stay on the sand and *occasionally* the glass (never the rock work), so I'm left with confusion and uncertainty haha :hmm4:
If there's a better camera angle I could provide, what would it be? I can take more photos tonight.