Both produce normal leaves (cordate in shape) in addition to the bullate leaves. The shell is bullate, fairly thick, white, spirally striate, with a well-developed periostracum. Three species develop bullate leaves which are hollow root-filled structures. Terms that describe vein prominence include bullate, channelled, flat, guttered, impressed, prominent and recessed ("Fig". The axils of lateral nerves and veins are conspicuously bullate above and dome-shaped.