Tandonia budapestensis (Hazay, 1881)
Medium slug, extended length 5 - 6 cm. Colour varies from yellowish-grey through browns to dark grey, with a reticulation of black spots. Very slender when fully extended and it contracts into a characteristic C-shape, not a hump. Pneumostome rimmed with black. Keel clear yellow or orange. Sole yellowish-white, usually with a darker central stripe, but sometimes darker at the sides. Mucus colourless.
When disturbed it contracts into a characteristic C-shape, and not into a "hump" as most other slugs do.
Mostly in parks, gardens and crops, in association with man. A notable pest.