Discus rotundatus (Müller, 1774):
Shell width of up to 7mm, with tightly coiled whorls. Shell is very flattened. Shell colour usually dark brown with reddish radial stripes/blotches. Deep radial ribs. Very common, especially in woods and hedges.The rotund disc snail is very small. It is approximately 2.5 mm in height and ranges in width from 5.5-7.2 mm, with about 4.5-6 whorls. This flattened shell is almost disc-shaped and can either be grey or light yellow-brown in color, with prominent uniformly arranged reddish brown blemishes. The body of the animal is blue-grey or blue-black, but pale on the sides of the foot.
By Hectonichus (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons
By Francisco Welter Schultes [CC BY-SA 2.5], via Wikimedia Commons