About Steromphala pennanti (R.A.Philippi, 1846)
The shell of Steromphala pennanti ranges in size from 10 mm to 16 mm. Compared to Gibbula cineraria, its shell is more depressed, with a flatter base, and never takes on a pyramidal shape. Its spiral ridges are sharper and fewer in number, a trait that is especially noticeable in young individuals. Steromphala pennanti is typically broader and has a wider umbilicus than Gibbula cineraria. The two species have similar general types of markings, but their color patterns differ. In Steromphala pennanti, the longitudinal streaks or rays are red, broader, and far fewer in number than those of Gibbula cineraria. These markings are sometimes zigzag, rather than broken into spots or interrupted by the shell's sculpture. Overall, Steromphala pennanti has striped markings, while Gibbula cineraria has fine lined markings. Just inside the outer lip of the shell, there are two borders: one is yellow, and the other is green with red spots. This lip edging is covered in tiny tubercles that give it a shagreen texture. This species is found in the North Sea and in waters off the coast of Spain.
