I found this on a divers' forum & nobody can identify it. A gastropod. Can't send pictures. Several spotted by divers in Roatan, Honduras & Cozumel, Mex. Descrïption: 12" or more (this is puzzling, but verified by more than 1 diver). Color: Seems dark blue/black, but may be different due to depth where sighted. A large snail. From above it looks a bit like a nerite or moon snail. The spire is like a True Tulip. The animal is large, seemingly black with white or light blue streaks. No synphon, so it's not a Tulip. Looks a bit like a Partridge Tun. But the size?????? Thanks in advance.
Oh, the entire outer shell has a fine checkerboard design.
Hi Tom,
I must say the various points of the descrïption are a bit confusing. The only two species in that area that actually reach a foot in shell length are Cassis madagascariensis and Pleuroploca gigantea.  The Cassis doesn't have an elongate siphon, but it has practically no spire either, certainly not a spire "like a True Tulip".  The Pleuroploca has a spire like a True Tulip, but also a very obvious long siphon. For the sake of discussion, let's forget "12" or more" and assume that "things look bigger underwater".  Other species in the area that exceed 8 inches include Cassis tuberosa, Tonna galea, and Charonia variegata.  The first two, while they lack an elongate siphon, have a flat or nearly flat spire.  The only one I can think of that has a tall spire without an elongated siphon is Charonia variegata, which also has an intricate pattern that might appear "checkered" underwater.  However, I can't imagine any Caribbean diver not recognizing that species!  So, I'm at a loss!
Is there a picture on that divers' forum? Â <span class="petit">--Last edited by Paul Monfils on 2010-02-04 02:36:09 --</span>
Paul, Long time no see. Thanks again. The one's you listed are ones I thought of as the only 12" ones in the Carib. But it's not any of those. One diver put his hand next to it to confirm  that it actually was so big. Anyway the pictures are at: ScubaBoard.com  Go to forums and then down a bit to Basic Scuba Discussions. At present it is on page 2 and titled "Help Identifying Snail". You can also read all the posts from the divers. Good luck....TH
I believe it's Tonna galea.
Here's the link to the picture on the scuba site:
<a href="http://www.scubaboard.com/forums/basic-scuba-discussions/321709-help-identifying-snail.html" target="_blank"><!-- m --><a class="postlink" href="http://www.scubaboard.com/forums/basic-scuba-discussions/321709-help-identifying-snail.html">http://www.scubaboard.com/forums/basic- ... snail.html</a><!-- m --></a>
and a link to another picture of the same species:
<a href="http://images.google.com/imgres?imgurl=http://i94.photobucket.com/albums/l110/olram9/Tonnidae/Tonna6.jpg&imgrefurl=http://205606.aceboard.net/205606-2058-8224-0-Tonna-galea.htm&usg=__FY8QHyH90xn8TBrYu9QxB8gDxus=&h=548&w=800&sz=55&hl=en&start=21&um=1&itbs=1&tbnid=fnpMe6m0kOcKUM:&tbnh=98&tbnw=143&prev=/images%3Fq%3D%2522Tonna%2Bgalea%2522%26hl%3Den%26lr%3D%26sa%3DN%26um%3D1" target="_blank"><!-- m --><a class="postlink" href="http://images.google.com/imgres?imgurl=http://i94.photobucket.com/albums/l110/olram9/Tonnidae/Tonna6.jpg&imgrefurl=http://205606.aceboard.net/205606-2058-8224-0-Tonna-galea.htm&usg=__FY8QHyH90xn8TBrYu9QxB8gDxus=&h=548&w=800&sz=55&hl=en&start=21&um=1&itbs=1&tbnid=fnpMe6m0kOcKUM:&tbnh=98&tbnw=143&prev=/images%3Fq%3D%2522Tonna%2Bgalea%2522%26hl%3Den%26lr%3D%26sa%3DN%26um%3D1">http://images.google.com/imgres?imgurl= ... N%26um%3D1</a><!-- m --></a>
. Â <span class="petit">--Last edited by Paul Monfils on 2010-02-04 05:15:29 --</span>
It must be that. Â They can reach 10". The only thing that looked different was the (apparent) heaight and whorls on the spire. Thanks.
I must admit that the shape and pattern do look like a huge Tonna maculosa rather than galea. Galea is much more globose and has a plain colour rather than the 'checkerboard' pattern which is indicative of maculosa or perdix.
There is always the outside possibility that it is a new species. What is needed is a specimen, did anyone find an empty shell rr take a live one?.
Dave
No Dave. They're typical divers of today- "Take only pictures, leave only bubbles".
Shame. Don't get me wrong that philosophy is very laudable but in situations such as this a voucher specimen is necessary for determination of a species. It could well be new to science but we shall neven know unless someone actually takes a specimen.
Dave