Steromphala umbilicalis

Steromphala umbilicalis, common name the flat top shell, is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails.

Description
The size of an adult shell varies between 10 mm and 22 mm. The shell is more depressed than Gibbula cineraria, and (although the base is flatter) never inclined to a pyramidal form. The spiral ridges are sharper and fewer, especially in the young. The coloring is different; both have a similar kind of marking, but in the present species the longitudinal rays or streaks are red, besides being broader and not half so many as in the other species. They are sometimes zigzag, instead of being broken into spots or interrupted by the sculpture. This species is striped, the other lineated. Just within the outer lip are two borders, one of yellow, the other of green variegated by red spots. This edging is minutely tubercled like shagreen.

Distribution
This marine species occurs in European waters and in the Mediterranean Sea off Morocco. It is found from the upper shore into the sublittoral on sheltered rocky shores and is tolerant of emersion and brackish waters.