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Helmet Seashells

Updated on December 25, 2012
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Bronwen and her family have enjoyed collecting many things, including fans, clocks, books and shells.

Gastropoda and Caenogastropoda

The designations of Gastropoda and Caenogastropoda can be a little confusing.

The Order of Gastropoda: There used to be over one hundred families that were classified as belonging to the traditional Order of Gastropoda, as it was once known. This Order included most of the well known sea snails, freshwater snails and land snails.

The Superorder of Caenogastropoda: Some years back these animals were reclassified and they are now placed in the Superorder of Caenogastropoda. This taxonomy, or particular scheme of classification, was first established as a superorder in 1960 by Leslie Reginald Cox.

The Unique Superorder of Caenogastropoda: This Superorder includes molluscs that are unique in several ways.

  • The gill, kidney and olfactory organ only exist on their left side
  • The heart only has one atrium and one ventricle.
  • The Excretory and reproductive ducts are separate.
  • Most of the animals produce egg capsules and these may contain from one to over a thousand eggs.

Two Main Groups of Caenogastropoda: The two main groups of Caenograstropoda have been classified according to the anatomy of the creature's radula. This is a horny structure that is found in the mouths of all molluscs, except bivalves, and is sometimes erroneously referred to as its tongue. It is a ribbon-like structure that is made up of minute horny teeth and is rather like sandpaper. It is used for feeding and for drilling into the shells of other molluscs.

  1. Taeniglossa: The radula usually has seven teeth in each row.
  2. Stenoglossa: The radula has only one to three teeth in each row.


Helmet (Underside)
Helmet (Underside) | Source

The Family Cassidae: Helmets and Bonnets

The family Cassidae is made up of around sixty species that live in tropical and temperate seas around the world. The shells grow to either a medium or large size and are sought after by collectors.

Cassidae family members range from the Helmets, which are quite large, to the smaller Bonnet seashells.

Helmet Seashell
Helmet Seashell | Source

Helmet Seashells

Helmet Seashells feed mostly on members of the sea urchin family.

During the day the Helmet lies buried and dormant in the sandy bottom, from fairly shallow tidal areas down to seas about a hundred metres deep. At night it comes out to feed and is quite active, crawling over the sand and reefs. It can sense a sea urchin from a short distance away. It climbs onto it, protected from the urchin's spines by its tough foot.

The Helmet uses its radula 'teeth', combined with special acidic secretions, to drill a hole in the shell of the sea urchin. It then sucks out and digests the soft parts of the animal from inside the urchin's shell.

The Helmet has been used for the making of cameos and also as lampshades, sometimes carved, and even as doorstops. They have been popular for collectors and this has resulted in a significant reduction in their occurrence. They are now protected in Australian waters, especially as it was thought that they could feed on the Crown of Thorns, a sea star that has been devastating the coral on the Great Barrier Reef.

Vibex Bonnet
Vibex Bonnet | Source

Bonnet Seashells

Bonnet seashells are smaller than the Helmets. They have similar characteristics to the Helmets in that the males are smaller.

Bonnet seashells are quite varied in pattern; in the images provided here the vibex has some pretty markings, the striped is quite eye-catching and the channelled has interesting markings from the very top to the base. As they are very attractive, they, too, are collectible.

Striped Bonnet
Striped Bonnet | Source
Channelled Bonnet
Channelled Bonnet | Source

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    • phoenix2327 profile image

      Zulma Burgos-Dudgeon 4 years ago from United Kingdom

      A very good read accompanied by beautiful pictures. What more could you want in a hub. Lovely job, Blossom.

    • bluebird profile image

      bluebird 4 years ago

      Very interesting, seashells have always amazed me but I've never taken the time to study them as you have obviously. Thanks for sharing this information. This is a good hub and well done.

    • BlossomSB profile image
      Author

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      phoenix2327: Thank you for your lovely comments. I hope you had a great Christmas.

      bluebird: I guess I can thank my Mother for that. She was always encouraging us to collect shells along the beach and to learn about them. I'm glad you enjoyed it.

    • profile image

      Marcia Ours 4 years ago

      Interesting article about seashells. Great pictures, too! Hope you had a Merry Christmas, and Happy New Year!

    • Genna East profile image

      Genna East 4 years ago from Massachusetts, USA

      Beautiful shells, Blossom. I love the striped bonnets. When we pick up these shells from the beaches, they are empty and lifeless, so it was especially interesting to learn about how they live in their water homes.

    • AudreyHowitt profile image

      Audrey Howitt 4 years ago from California

      Such beautiful shells Blossom--thank you for providing so much information on how these creatures live--

    • Lipnancy profile image

      Nancy Yager 4 years ago from Hamburg, New York

      Shells are so cool. You can look at them forever and always see something different.

    • BlossomSB profile image
      Author

      Bronwen Scott-Branagan 4 years ago from Victoria, Australia

      marcia Ours: Glad you enjoyed it. Thank you, I had a lovely Christmas, hope you did too, and wishing you a great New Year.

      Genna East: Yes, they're unusual and pretty, too. It's fascinating to watch them on the sandy bottom. Much more interesting than land snails that just eat my vegetables!

      AudreyHowitt: Thank you. They are such interesting animals.

      Lipnancy: They're lovely to look at and I love the feel of them, too.

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