Size to 6 mm. Animal covered with papillae of variable sizes arranged in two main groups, dorso-lateral and median-dorsal papillae. Three bipinnate gills present. Sides of the head forming a ridge sometimes marked with projections. Ridge may be prolonged along sides of body as series of papillae. Color green or gray with green, brownish, and yellowish flecks. Photo by Ángel Valdés.