Occasionally I'll see images of sundial snails on Reef Central. I'd never seen one in person until today. While buying some zoanthids at the LFS, I picked up a frag and found it underneath. Sundial Snails are predators and will eat zoanthids greedily.

If you own zoos, you would be wise to study your colonies late night when the coral is closed up to see if these snails are in your tank.

The shell markings are very recognizable. And interestingly enough, the two antennae that they extend appear to be tattooed, just like whelks (another predator that eats clams).

Since there doesn't seem to be a lot of documentation, or should I say there is usually a lack of pictures available, this thread is going to provide all the images I took today. I found one at one LFS, then went to another store and found two more.

First of all, these are very small. It is hard to state their size in comparison to something else, so let's use measurements. The three I have are 3/8" wide (diameter of the shell) and 1/8" thick. Since they can breed and produce babies, you may find tinier ones. Here is what they look like.

This is a view from above. Much to my surprise, they travel on their edge, with the disk standing perpendicular to the surface they are affixed to. With all the images I've seen, I never knew they did this.

Here are two more pictures of the snail next to a common dime.

And once with the snail on the dime. The strange pointy thing that looks like a rattlesnake rattle doesn't appear to do anything more than retract within the shell when the snail goes to hide.

Here are a couple of them in a small disposable serving container. If you are a Domino's Pizza fan, you may recognize this as the individual serving dish they'll fill with jalapenos, for example.

All three in that same serving dish. I put a thumbscrew in the water with them. If you own a calcium reactor or protein skimmer, you may have seen these black nylon screws. If so, maybe you can get a good idea how small these snails are.

Here is a close up, showing how those feelers appear to be tattoed. (Take a look at this article about whelks to see what I mean: http://melevsreef.com/id/whats_a_whelk.html )

Here is another shot of two showing their funny 'tail'.

Hope that helps.