Semilimax semilimax is a semi-slug with central European and Alpine distribution. It lives in moist forests. It is from the family Vitrinidae.
Left side view:
Right side view:
When I found those gastropods, I though, that I found two different species. Unfortunately all of them are the same species – Semilimax semilimax. I realized that in the lab some time later.
Six semi-slugs, five dark grey, one light grey and all of them are Semilimax semilimax:
It is exactly as Welter Schultes wrote: “Animal light to dark grey”. They can vary in color even in one population as it is documented in this my record from central Moravia.
Horsák M., Juřičková L. & Picka J. (2013) Měkkýši České a Slovenské republiky. Molluscs of the Czech and Slovak Republics. Kabourek, Zlín, 264 pp. (in Czech and English). page 34 and page 111.
Welter Schultes F. (2013) Species summary for Semilimax semilimax. AnimalBase, last change 11 December 2013, accessed 28 November 2016.
These are three gastropods from the family Vitrinidae on a human hand. Each of them belong to a different genus. All of them shows a different level of a reduction of its shell.
The upper one is Vitrina pellucida. This gastropod can completely withdraw into its shell and therefore it is called a snail.
Two others can not fully withdraw into their shells. They are semi-slugs.
The lower left is Eucobresia diaphana. Mantle covers apical part of the shell.
The lower right is Semilimax semilimax. Quite big mantle lobe is covering an apex. The reduction of the shell of Semilimax semilimax is the highest among these three species.
Genera in the family Vitrinidae shows the complete example of the shell reduction from the snails through semi-slugs to slugs.
Examples of snails: Phenacolimax, Vitrina.
Examples of semi-slugs: Eucobresia, Semilimax, Vitrinobrachium.
Example of a slug in Vitrinidae is Plutonia atlantica. It is a slug with an internal shell living on Azores.
Species summary for Plutonia atlantica. AnimalBase, accessed 2 January 2014.
Species summary for Vitrina pellucida. AnimalBase, accessed 2 January 2014.