The shell has dimensions ranging from 48.7 to 56.0 mm in length, 26.6 to 28.6 mm in height, and 19.3 to 21.2 mm in width. It is elongated and notably inflated, with prominent umbones. The lateral teeth are straight, and the ventral margin forms a straight line. The periostracum is dark brownish to deep green. It can be distinguished from R. caerulea by its shorter and more swollen shell, and it differs from R. bonnetutdi by its thickness and the characteristic dark brownish periostracum with prominent green striae.