This is the "musical" freshwater diatom, Terpsinoë musica, seen in girdle view. the "notes" are silica septa, ingrowths of the wall. The cells are corrugated in valve view and attached to each other by mucilage pads at diagonal corners to form zig-zag, crinkle-cut chains (see http://mangilao.uog.edu/classes/botany/ ... psinoe.htm).
