Snail Shells

Snail shells are made of calcium carbonate and small amounts of protein. Snails make their shell gradually over time. The shell is then covered by a hard, shiny layer of protein called periostracum. The shell is built from a skin line material, just under the shell called the mantle. The mantle releases the materials that will form a shell and these materials will harden to make the very hard shell. The mantle continues to release liquids so the shell continues to grow.

The snail will go inside its shell if it feel threatened or like an enemy is close by. Snails can't move very fast at all so they would not be able to escape a predator any other way other then to hide in its hard shell. The snail can then close off the opening to the shell to stop anything getting inside. It can either do this by pushing the hard part of its foot against the opening or creating a slime that can harden to cover the hole. The snail can stay inside the shell for days or even weeks at one time. The snail may also decide to go inside its shell is the weather conditions are either really cold or really hot so that they can keep themselves moist. They barely move during this time so they need hardly any food or drink to stay alive and healthy.

The texture of a shell feels very harsh and slightly rough. The very small and fine ridges in the shell make it feel slightly rough if you run your finger against them; however if you run them along the lines then they feel very smooth. The snail shell usually has about four to five spirals. The colouring of a snail shell is very much dependant on the type of snail, however the Polymita Picta snail shells are very bright and colourful. The shells twist into a spiral in the middle to a point and the colouring of them follow that curved pattern. The lines are very straight and even as the twist upwards, making them look very neat and almost artificial.

Polymita Picta Snail Shell
VIOLA, 2015. Painted snail Polymita picta [7 November 2015]. 
Available from: http://vsemart.com/painted-snail-polymita-picta/

Resources:
DK Publishing, 2008. Animals A Visual Encyclopedia. 1st ed. New York: Credo Reference

HOWSTUFFWORKS, 2015. Snail [5 November 2015]. Available from: http://animals.howstuffworks.com/marine-life/snail-info.htm

ORSTAN, A., 2005. Snail Shells are made of this. In: Snail's Tales. 11 November 2005 [7 November 2015]. Available from: http://snailstales.blogspot.co.uk/2005/11/snail-shells-are-made-of-this.html