Shell less ponderous than R. niloticus; form strictly conical; whorls of the spire decidedly plicate or tuberculide, planulate; body-whorl not dilated at the periphery; base flat, concentrically grooved; columella less oblique than in the type. Alt. 95, diam. R. maximus is an arrested or primitive form of niloticus. In the conic form, flat, lirate base, and sculptured spire, it exactly resembles an immature specimen of the latter species ; but at the same time, it retains these characters in adult individuals. I do not know whether both occur in the same locality; if they do, I would incline to consider them distinct. The finest suite I have seen of the T. maximus is from the Viti Is., collected by the late ANDREW GARRETT.