The dorsal margin is slightly biundulate in larger valves. The dorsal margin of smaller valves is almost flat. At the smallest end of the size range, the dorsal margin is convex. The valve apices are bluntly rounded and slightly “set off” by a gradual change in slope of the dorsal margin. The striae are mostly parallel and curved towards the apices distal to the the helictoglossa. often with a few irregular, short striae on the dorsal margin.
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