Echinolittorina meleagris (Potiez and Michaud, 1838) White-spot Periwinkle

Echinolittorina meleagris (Potiez and Michaud, 1838) White-spot Periwinkle
With barnacles on rocks, near high-water, N. edge of N. jetty at Ft. Pierce Inlet, St. Lucie Co., FL (4 mm.)