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.