Genus Notoplax H. Adams, 1861

Type species. Cryptoplax (Notoplax) speciosa H. Adams, 1861, by monotypy.

Diagnosis. Medium to large chitons. Tegmentum reduced, with well defined, narrow jugum; lateral and pleural areas separated by larger pustules on diagonal line. Articulamentum large; sutural laminae convex in antero-lateral edge in tail valve; insertion plates large on all valves; slit formula 5/1/3-10. Girdle large, thick, very fleshy, densely spiculose, completely (rarely almost completely) encroaching between valves; sutural tufts always present, but usually not prominent (after Gowlett-Holmes 1991, with modification). Radula teeth arranged in skewed rows; central tooth asymmetrical, large, rectangular, concave in the distal half, bilobed at base; first lateral (centro-lateral) tooth with thin, weakly notched antero-dorsal corner; major lateral tooth with long median denticle in large tricuspid head (after Saito 2004 with modification).